Flexible beamforming for satellite communications

ABSTRACT

Systems and methods for supporting more flexible coverage areas and spatial capacity assignments using satellite communications systems are disclosed. A hub-spoke, bent-pipe satellite communications system includes: terminals; gateways; a controller for specifying data for controlling satellite operations in accordance with a frame definition including timeslots for a frame and defining an allocation of capacity between forward and return traffic. The satellite communications system may employ a satellite with a feed array assembly and may use on-board beamforming or ground-based beamforming. Beam hopping within timeslots of the frame may be used to provide coverage to different cells in different time periods. The flexible coverage areas may be provided using changes in satellite position, antenna patterns, or beam resource allocations.

CROSS REFERENCES

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/887,147, filed on Oct. 19, 2015, entitled “Flexible CapacitySatellite Communications System,” which is a continuation of U.S. patentapplication Ser. No. 13/666,112, filed on Nov. 1, 2012, entitled“Flexible Capacity Satellite Communications System,” which is acontinuation of PCT Application No. PCT/US2011/034845, filed on May 2,2011, entitled “Flexible Capacity Satellite Communications System,”which claims priority to U.S. patent application Ser. No. 13/098,334,filed on Apr. 29, 2011, entitled “Flexible Capacity SatelliteCommunications System with Flexible Allocation Between Forward andReturn Capacity,” and U.S. patent application Ser. No. 13/098,213, filedon Apr. 29, 2011, entitled “Flexible Capacity Satellite CommunicationsSystem with Dynamic Capacity Distribution and Coverage Areas,” each ofwhich claims the benefit of priority under 35 U.S.C. § 119(e) of U.S.Provisional Application Nos. 61/330,377, filed on May 2, 2010, and61/375,384, filed on Aug. 20, 2010, both entitled “Flexible CapacityCommunication Satellite System”; the entireties of all of which areherein incorporated by reference for any and all purposes.

BACKGROUND

Communications satellites typically include one or more antennaassemblies for communicating with various terrestrial target devices,which may include ground-based access node terminals or user terminals,any of which may be stationary (e.g., installed at a permanentinstallation site, moved from one fixed installation site to another,etc.) or mobile (e.g., installed at a vehicle, a boat, a plane, etc.).An antenna assembly of a communications satellite may be configured fortransmitting downlink signals (e.g., forward link signals to userterminals, return link signals to access nodes) and/or receiving uplinksignals (e.g., forward link signals from access nodes, return linksignals from user terminals). The antenna assembly may be associatedwith a service coverage area within which devices may be provided acommunications service via the antenna assembly. The satellite may be ageostationary satellite, in which case the satellite's orbit issynchronized with the rotation of the Earth, keeping the servicecoverage area essentially stationary with respect to the Earth. In othercases, the satellite is in an orbit about the Earth that causes theservice coverage area to move over the surface of the Earth as thesatellite traverses its orbital path.

Some satellite communication systems employ “bent-pipe” satellites thatrelay signals among terminals located in the same antenna footprint(e.g., service coverage area), for example, the continental UnitesStates. In circumstances where transmit and receive coverage areas areoverlapping, separate frequency bands and/or polarizations may be usedfor the uplink (to the satellite) and the downlink (from the satellite).The “bent-pipe” designation refers to the fact that the relayed signalsare effectively retransmitted after the signals are received by thesatellite, as if redirected through a bent pipe. The data in the relayedsignals is not demodulated or remodulated as in a “regenerative” orprocessing satellite architecture. Rather, signal manipulation on thesatellite in a bent-pipe architecture is generally limited to functionssuch as frequency translation, filtering, amplification, and the like.

Other satellite communication systems were developed around satellitesthat employ innovations such as digital channelization and routing ofsignals, demodulation/routing/re-modulation of the data in the relayedsignals, narrow antenna footprint spot beams to allow frequency reuse,and phased array antennas to allow dynamic placement of coverage areas.

For example, satellites for Mobile Satellite Services (MSS) typicallyemploy spot beam coverage areas with a greater degree of frequencyreuse. Examples of satellites for MSS include the Inmarsat-4 satellitesand the Thuraya satellites. These satellites typically feature a largenumber of narrow spot beams covering a large composite area and allowfor flexible and configurable allocation of bandwidth. However, thetotal system bandwidth is low (such as a 34 MHz allocation at L-band),and service is generally categorized as “narrow band” (e.g., carrierbandwidths of hundreds of kHz), which allows the flexible andconfigurable bandwidth allocation to be accomplished using digitalbeamforming techniques. These satellites use a large reflector with anactive feed array. The signals associated with each antenna feed elementare digitized, and the beamforming and bandwidth flexibility areprovided by a digital signal processor. The digital beamforming isperformed on narrowband channels, allowing any narrowband channel on thefeeder link to be placed at any frequency for any spot beam shape.

The Wideband InterNetworking Engineering Test and DemonstrationSatellite (WINDS) is an experimental Ka-band satellite system. Thesatellite implements both fixed spot beams using a fixed multi-beamantenna (MBA) and steerable beams using an active phased array antenna(APAA). The MBA serves fixed beams, and the communications link can beswitched over time in a pattern consisting of combinations of receivingand transmitting beams. The APAA has been developed as a beam-hoppingantenna with a potential service area that covers almost the entirevisible region of earth from the satellite. The APAA can provisioncommunications between arbitrary users using two independently steerablebeams for each of the transmitting and receiving antennas. Beam steeringis achieved by updating pointing directions via control of digital phaseshifters in switching interval slots as short as 2 ms in SatelliteSwitched Time Division Multiple Access (SS-TDMA) mode, where theshortest beam dwell time corresponds to the slot time of the SS-TDMAsystem. Beam switching at high speed is supported for up to eightlocations per beam. Switching patterns for both the MBA and APAA areuploaded from a network management center.

Spaceway is a Ka-band satellite system that services 112 uplink beamsand nearly 800 downlink beams over the United States. The Spacewaysatellite uses a regenerative on-board satellite processor to route datapackets from one of 112 uplink beams to one of nearly 800 possibledownlink beams. At any time the downlink consists of up to 24 hoppingbeams. The downlink scheduler determines which beams should betransmitting bursts for each downlink timeslot depending on each beamsdownlink traffic queue and power and interference constraints.

The Wideband Global SATCOM (WGS) satellite, formerly known as theWideband Gapfiller Satellite, is a U.S. government satellite thatemploys steerable Ka-band spot beams and X-band beamforming. The Ka-bandspot beams are mechanically steered. Up to eight X-band beams are formedby the transmit and receive X-band arrays using programmable amplitudeand phase adjustments applied to beamforming modules (BFMs) in eachantenna feed element. Bandwidth assignment is flexible and configurableusing a broadband digital channelizer, which is not involved inbeamforming.

More recent satellite architectures have resulted in further increasesin system capacity. For example, ViaSat-1 and the Ka-band spot beamsatellite architectures disclosed in Dankberg et al. U.S. Pat. App. Pub.No. 2009-0298416, which is incorporated by reference herein in itsentirety, can provide over 150 Gbps of physical layer capacity. Thisspot beam architecture provides over an order of magnitude capacityincrease over prior Ka-band satellites. Other satellites, for exampleKA-SAT and Jupiter, use similar architectures to achieve similarly highcapacities. The architecture used in all of these satellites is a “bentpipe” hub-spoke architecture that includes small spot beams targeted atfixed locations. Each spot beam may use a large amount of spectrum,typically 250-1000 MHz. The resulting large capacity is a product ofseveral characteristics of the satellite system, including, for example,(a) the large number of spot beams, typically 60 to 80 or more, (b) thehigh antenna directivity associated with the spot beams (resulting in,for example, advantageous link budgets), and (c) the relatively largeamount of bandwidth used within each spot beam.

The aforementioned high capacity satellite architectures are valuable,but may still be limited in certain respects. For example, scaling thearchitecture to support higher capacities while maintaining the samespectrum allocation and power budget is typically accomplished usinglarger reflectors to create spot beams with smaller diameters. The useof smaller diameter spot beams may increase the directivity (or gain) ofthe satellite antenna, thus enhancing the link signal-to-noise ratio(SNR) and capacity. However, the smaller spot beams necessarily reducethe service coverage area (e.g., the coverage area for which acommunications service can be provided). These satellite architectures,therefore, have an inherent tradeoff of capacity versus coverage area.

In addition, these architectures typically place all spot beams, bothuser beams and gateway (GW) beams, in fixed locations. There isgenerally no ability to move the spot beams around to accommodatechanges in the service coverage area. Moreover, the architecturesessentially provide uniformly distributed capacity over the servicecoverage area. The capacity per spot beam, for example, is stronglyrelated to the allocated bandwidth per spot beam, which is predeterminedfor every spot beam and allows for little to no flexibility orconfigurability.

Although these satellite communications architectures are valuable whenthe desired service coverage area is well-known and the demand forcapacity is uniformly distributed over the service coverage area, theinflexibility of the aforementioned architectures can be limiting forcertain applications. For example, a communications satellite may beretasked or deployment conditions (e.g., orbital slot, etc.) may change.Additionally, a satellite communications service may see changes in userdemands (e.g., fixed vs. mobile users, etc.). Although signal processingtechniques such as beamforming may provide some ability to adapt thearrangement of spot beams or service coverage area, additionalflexibility in adaptation of service coverage area and spot beamarrangement may be desired. For example, it may be desirable for asatellite communications system architecture to support flexibility inthe locations and sizes of spot beam coverage areas, the locations ofuser terminals and access node terminals, the spatial distribution ofthe communications service capacity, and the capacity allocation of thecommunications service. Further, it may be desirable to support suchflexibility along with changes in orbital position of a communicationssatellite or allow moving a communications satellite to another orbitalslot during the mission lifetime.

SUMMARY

In view of the foregoing, aspects for providing flexible satellitecommunications are described.

An example of a hub-spoke, bent-pipe satellite communications systemincludes: multiple user terminals; multiple access node terminalsconfigured to communicate with the multiple user terminals; a controllerconfigured to specify data for controlling satellite operations inaccordance with a frame definition, the frame definition includingmultiple timeslots for a frame and defining an allocation of capacitybetween forward traffic, from at least one access node terminal tomultiple user terminals, and return traffic, from multiple userterminals to at least one access node terminal; and a communicationssatellite including: multiple pathways; at least one low noise amplifier(LNA), wherein an output of the at least one LNA is configured to becoupled to a pathway of the multiple pathways and to amplify uplink beamsignals in accordance with the allocation of capacity between forwardtraffic and return traffic defined by the frame definition; and at leastone high power amplifier (HPA), wherein an input of the at least one HPAis configured to be coupled to the pathway of the multiple pathways andto amplify downlink beam signals in accordance with the allocation ofcapacity between forward traffic and return traffic defined by the framedefinition, and wherein the frame definition specifies configuration ofat least one pathway of the multiple pathways as a forward pathway forat least one timeslot in the frame, and configuration of the at leastone pathway as a return pathway for at least one other timeslot in theframe.

Embodiments of such a satellite communications system may include one ormore of the following features. The communications satellite furtherincludes one or more beamforming networks configured to couple theoutput of the at least one LNA to the pathway of the multiple pathwaysand to couple the input of the at least one HPA to the pathway of themultiple pathways. The communications satellite further includes aphased array of antenna feed elements, and an input of the at least oneLNA is configured to be coupled to an output of an antenna feed elementof the phased array. The communications satellite further includes aphased array of antenna feed elements, and at least one harmonic filter,wherein an output of the at least one harmonic filter is configured tobe coupled to an input of an antenna feed element of the phased array,and an output of the at least one HPA is configured to be coupled to aninput of the at least one harmonic filter.

An example of a method for hub-spoke, bent-pipe satellite communicationsutilizing a communications satellite containing multiple pathways and incommunication with multiple user terminals and multiple access nodeterminals, includes: at a controller, specifying data for controllingcommunications satellite operations in accordance with a framedefinition, the frame definition including multiple timeslots for aframe and defining an allocation of capacity between forward traffic,from at least one access node terminal to multiple user terminals, andreturn traffic, from multiple user terminals to at least one access nodeterminal; and at the communications satellite, receiving uplink beamsignals and transmitting downlink beam signals in accordance with theallocation of capacity between forward traffic and return trafficdefined by the frame definition, and wherein the frame definitionspecifies configuration of at least one pathway of the multiple pathwaysas a forward pathway for at least one timeslot in the frame, andconfiguration of the at least one pathway as a return pathway for atleast one other timeslot in the frame.

An example of a communications satellite for hub-spoke, bent-pipesatellite communications includes: multiple pathways; at least one lownoise amplifier (LNA), wherein an output of the at least one LNA isconfigured to be coupled to a pathway of the multiple pathways and toamplify uplink beam signals in accordance with an allocation of capacitybetween forward traffic, from at least one access node terminal tomultiple user terminals, and return traffic, from multiple userterminals to at least one access node terminal, defined by a framedefinition, the frame definition including multiple timeslots for aframe; and at least one high power amplifier (HPA), wherein an input ofthe at least one HPA is configured to be coupled to the pathway of themultiple pathways and to amplify downlink beam signals in accordancewith the allocation of capacity between forward traffic and returntraffic defined by the frame definition, and wherein the framedefinition specifies configuration of at least one pathway of themultiple pathways as a forward pathway for at least one timeslot in theframe, and configuration of the at least one pathway as a return pathwayfor at least one other timeslot in the frame.

Embodiments of such a communications satellite may include one or moreof the following features. The communications satellite further includesone or more beamforming networks configured to couple the output of theat least one LNA to the pathway of the multiple pathways and to couplethe input of the at least one HPA to the pathway of the multiplepathways. The communications satellite further includes a phased arrayof antenna feed elements, wherein an input of the at least one LNA isconfigured to be coupled to an output of an antenna feed element of thephased array. The communications satellite further includes a phasedarray of antenna feed elements, and at least one harmonic filter,wherein an output of the at least one harmonic filter is configured tobe coupled to an input of an antenna feed element of the phased array,and an output of the at least one HPA is configured to be coupled to aninput of the at least one harmonic filter.

An example of a method for hub-spoke, bent-pipe satellite communicationsutilizing a communications satellite containing multiple pathways and incommunication with multiple user terminals and multiple access nodeterminals, where the method is performed at the communicationssatellite, includes: receiving uplink beam signals; and transmittingdownlink beam signals, wherein receiving the uplink beam signals andtransmitting the downlink beam signals are in accordance with anallocation of capacity between forward traffic, from at least one accessnode terminal to multiple user terminals, and return traffic, frommultiple user terminals to at least one access node terminal, defined bya frame definition, the frame definition including multiple timeslotsfor a frame, and wherein the frame definition specifies configuration ofat least one pathway of the multiple pathways as a forward pathway forat least one timeslot in the frame, and configuration of the at leastone pathway as a return pathway for at least one other timeslot in theframe.

In some examples, a communications satellite may be configured toprovide a communications service via one or more antenna assembliesaccording to different native antenna patterns, where each nativeantenna pattern may refer to a composite of the native feed elementpatterns for each of the plurality antenna feed elements of a respectiveantenna assembly in a given operating condition. Such antenna assembliesmay include a feed array assembly (e.g., a phased array of antenna feedelements), a reflector, and an actuator coupled between the feed arrayassembly and the reflector. The reflector may have a focal point orfocal region where radio frequency (RF) signals are concentrated whenreceived from a distant source. The feed array assembly may have aplurality of antenna feed elements for communicating signals associatedwith a communications service, and the reflector may be configured toreflect the signals transmitted between the feed array assembly and oneor more target devices (e.g., user terminals and/or access nodeterminals). The actuator may be a linear actuator having an adjustablelength, or may otherwise provide an adjustment in a relative distancebetween the feed array assembly and the reflector.

A feed array assembly may be positioned (e.g., using the linearactuator) in a region between the focal region and the reflector surfaceto operate as a defocused system where RF signals from a distant sourceilluminate a plurality of antenna feed elements. By adjusting theposition of the reflector relative to the feed array assembly from afirst defocused operating condition to a second defocused operatingcondition, the satellite may therefore provide a communications serviceaccording to different native antenna patterns for a respective antennaassembly. The adaptation of the native antenna patterns by in partchanging the defocused operating condition may improve the versatilityof the communications satellite by supporting additional adjustabilityin providing a desired coverage area, user beam characteristics,operating orbital position, or other coverage aspects.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter. The conceptionand specific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the scope of the appended claims. Characteristics of theconcepts disclosed herein, both their organization and method ofoperation, together with associated advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. Each of the figures is provided for the purpose ofillustration and description only, and not as a definition of the limitsof the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1A shows a diagram of a satellite communication system thatsupports flexible beamforming of satellite communications, in accordancewith aspects of the present disclosure;

FIG. 1B illustrates an antenna assembly of a communications satellitethat supports flexible beamforming of satellite communications, inaccordance with aspects of the present disclosure;

FIG. 1C illustrates a feed array assembly of an antenna assembly thatsupports flexible beamforming of satellite communications, in accordancewith aspects of the present disclosure;

FIGS. 2A through 2D illustrate examples of antenna characteristics foran antenna assembly having a feed array assembly located at a focalregion of a shaped reflector, in accordance with aspects of the presentdisclosure;

FIGS. 3A through 3D illustrate examples of antenna characteristics foran antenna assembly having a feed array assembly operating in adefocused position, in accordance with aspects of the presentdisclosure;

FIGS. 4A and 4B illustrate an example of beamforming to form spot beamcoverage areas from a native antenna pattern coverage area provided byan antenna assembly operating in a defocused condition, in accordancewith aspects of the present disclosure;

FIGS. 5A-5E illustrate an example of locations of spot beam coverageareas of a service coverage area during different communications servicetimeslots, in accordance with aspects of the present disclosure;

FIG. 6 shows an illustrative beam hopping frame, in accordance withaspects of the present disclosure;

FIG. 7 shows a block diagram for part of exemplary satellitearchitecture, in accordance with aspects of the present disclosure;

FIG. 8 shows block diagram of one polarization of an exemplary receivebeamforming network, in accordance with aspects of the presentdisclosure;

FIG. 9 shows block diagram of one polarization of an exemplary transmitbeamforming network, in accordance with aspects of the presentdisclosure;

FIG. 10 shows a block diagram of an illustrative system for ground-basedbeamforming for forward link signal transmission, in accordance withaspects of the present disclosure;

FIG. 11 shows a block diagram of an illustrative system for ground-basedbeamforming for return link signal reception, in accordance with aspectsof the present disclosure;

FIG. 12 shows block diagram of a system that employs an exemplary beamweight processor;

FIGS. 13A through 13C illustrate an example of a communicationssatellite having K=4 pathways, in accordance with aspects of the presentdisclosure;

FIG. 14 illustrates an example process for supporting satellitecommunication, in accordance with aspects of the present disclosure;

FIG. 15A shows an illustrative synchronized timeslot allocation, inaccordance with aspects of the present disclosure;

FIG. 15B shows an illustrative timeslot definition table andillustrative timeslot pathways, in accordance with aspects of thepresent disclosure;

FIG. 16A shows an illustrative interleaved timeslot allocation, inaccordance with aspects of the present disclosure;

FIG. 16B shows an illustrative timeslot definition table andillustrative timeslot pathways, in accordance with aspects of thepresent disclosure;

FIG. 17A shows an illustrative interleaved timeslot allocation, inaccordance with aspects of the present disclosure;

FIG. 17B shows an illustrative timeslot definition table andillustrative timeslot pathways, in accordance with aspects of thepresent disclosure;

FIG. 18A shows an illustrative dedicated pathways allocation, inaccordance with aspects of the present disclosure;

FIG. 18B shows an illustrative timeslot definition table andillustrative timeslot pathways, in accordance with aspects of thepresent disclosure;

FIG. 18C shows an illustrative timeslot definition table, in accordancewith aspects of the present disclosure;

FIG. 18D shows an illustrative timeslot definition table, in accordancewith aspects of the present disclosure;

FIG. 18E shows illustrative timeslot pathways, in accordance withaspects of the present disclosure;

FIG. 19 shows an illustrative chart of the number of access nodeterminals required versus the number of forward pathways allocated, inaccordance with aspects of the present disclosure;

FIG. 20A shows illustrative non-congruent forward and return linkservice coverage areas, in accordance with aspects of the presentdisclosure;

FIG. 20B shows illustrative timeslot pathways in accordance with aspectsof the present disclosure;

FIG. 21A shows an illustrative beam hop pattern of a single beam for thetimeslot dwell times of a beam hopping frame, in accordance with aspectsof the present disclosure;

FIG. 21B shows an illustrative timeslot dwell time table in accordancewith aspects of the present disclosure;

FIG. 21C shows an illustrative beam hopping frame in accordance withaspects of the present disclosure;

FIG. 22A shows illustrative access node terminal locations and user spotbeam locations in accordance with aspects of the present disclosure;

FIG. 22B shows an illustrative access node terminal table, in accordancewith aspects of the present disclosure;

FIG. 22C shows illustrative placements of access node terminallocations, in accordance with aspects of the present disclosure;

FIG. 23 is a simplified diagram of an illustrative satellitecommunications system, in accordance with aspects of the presentdisclosure;

FIGS. 24A through 24E illustrate changes to native antenna patterncoverage areas that may be supported by an antenna assembly, inaccordance with aspects of the present disclosure;

FIGS. 25A-25D illustrate communications satellites that supportsadjusting a relative position between a feed array assembly and areflector to support a change in native antenna patterns, in accordancewith aspects of the present disclosure;

FIGS. 26A-26F illustrate examples of communications satellites havingantenna assemblies with different types of actuators that may supportchanges in native antenna patterns, in accordance with aspects of thepresent disclosure;

FIG. 27 illustrates a block diagram of a communications satellite thatsupports providing a communications service according to a plurality ofnative antenna patterns, in accordance with aspects of the presentdisclosure;

FIG. 28 shows a block diagram of a satellite controller that supportsproviding a communications service according to a plurality of nativeantenna patterns, in accordance with aspects of the present disclosure

FIG. 29 shows a block diagram of a communications service manager thatsupports providing a communications service according to a plurality ofnative antenna patterns, in accordance with aspects of the presentdisclosure;

FIG. 30 shows a block diagram of a communications service controller3005 that supports providing a communications service according to aplurality of native antenna patterns, in accordance with aspects of thepresent disclosure; and

FIG. 31 illustrates a flow chart of an example method that supportsproviding a communications service via a communications satelliteaccording to a plurality of native antenna patterns, in accordance withaspects of the present disclosure.

DETAILED DESCRIPTION

A communications satellite may be configured to provide a communicationsservice between terrestrial target devices (e.g., terminals), which maybe stationary (e.g., installed at a permanent installation site, movedfrom one fixed installation site to another, etc.) or mobile (e.g.,installed at a vehicle, a boat, a plane, etc.). The communicationsservice may include, for example, bi-directional network access servicebetween access node terminals and user terminals. To support thecommunications service, one or more antenna assemblies of thecommunications satellite may be configured for transmitting downlinkcommunications (e.g., to user terminals or access node terminals),receiving uplink communications (e.g., from user terminals or accessnode terminals), or both transmitting downlink communications andreceiving uplink communications (e.g., operating as a transceiver).

Antenna assemblies of a communications satellite may include a feedarray assembly, such as phased arrays of antenna feed elements, whichmay be used to target beamformed spot beams on desired spot beamcoverage areas (e.g., cells) across a given system coverage geography(e.g., high population areas in North America). Beamformed spot beamsmay be formed from transmissions and/or receptions via a plurality ofthe antenna feed elements, and use phase and amplitude characteristicsof the transmissions and/or receptions to provide the directionaltransmission and reception associated with each of the beamformed spotbeams.

According to examples of the present disclosure, beamformed spot beamsmay hop from location to location according to weight vectors of abeamforming weight set and beam hop timeslot definitions included in abeam hopping frame definition. The beam hopping timeslot definitions mayinclude associated dwell times and pathway gains for all spot beamsduring one timeslot. The beam hopping timeslot definitions includedwithin a beam hopping frame definition may be automatically repeateduntil a new beam hopping frame definition is received or an interrupt issignaled, allowing for dynamic changes to the downlink service coveragearea, uplink service coverage area, and spot beam coverage arealocations.

A feed array assembly may have multiple feed elements for communicatingsignals (e.g., signals associated with a communications service,diagnostic and/or configuration signals for the communicationssatellite, etc.). Each feed element of the feed array assembly may beassociated with a respective native feed element pattern (e.g., a nativecomponent beam), which may provide a projected native feed elementpattern coverage area (e.g., as projected on a terrestrial surface,plane, and/or volume after reflection from the reflector). Thecollection of native feed element pattern coverage areas for a feedarray assembly of an antenna assembly may be referred to as a nativeantenna pattern.

Different characteristics of native antenna patterns may be desirablefor various operating conditions. For example, with broader native feedelement pattern coverage areas, a greater quantity of antenna feedelements of a feed array assembly may be able to support a particularspot beam coverage area. Moreover, broader native feed element patternsmay also allow each antenna feed element of a feed array assembly tosupport a greater quantity of beamformed spot beams. However, broadernative feed element patterns may have lower power density of radiation,and therefore it may be desirable to use narrower native feed elementpatterns in some cases. In some examples, a desired native antennapattern may be based at least in part on the orbital position of acommunications satellite.

According to aspects of the present disclosure, an antenna assembly of acommunications satellite may support operation at one of multiple nativeantenna patterns. For example, the communications satellite may providea communications service according to a first native antenna pattern ofan antenna assembly, and an actuator associated with the antennaassembly may subsequently be adjusted to provide a second native antennapattern of the same antenna assembly. Following the adjustment to theactuator, the communications satellite may therefore provide thecommunications service according to a second native antenna pattern,different from the first native antenna pattern. In various examples,the second native antenna pattern may be associated with a differentnative antenna pattern coverage area size, a different native feedelement pattern coverage area size (e.g., native feed element patternbeamwidth) and/or position, a different degree of overlap of native feedelement pattern coverage areas, a different spot beam size (e.g.,beamwidth), a different spot beam coverage area size and/or position, adifferent degree of overlap of spot beams, different beamforming weightsets, or any combination thereof, than those of the first native antennapattern.

In some examples, an antenna assembly of a communications satellite mayinclude a feed array assembly, a reflector, and an actuator coupledbetween the feed array assembly and the reflector. The reflector may beshaped to have focal region (e.g., a focal point), and the reflector maybe configured to reflect the signals transmitted between the feed arrayassembly and one or more target devices (e.g., access node terminalsand/or user terminals). The actuator may, for example, include a linearactuator that provides a change in length, thereby providing a change inrelative position between the feed array assembly and the reflector(e.g., a different position with reference to the focal region of thereflector). In some examples a communications satellite may include botha linear actuator and a second actuator to provide an additional degreeof freedom between the feed array assembly and the reflector. In suchexamples, the second actuator may be commanded to cause a change inrelative position between the feed array assembly and the reflectorabout an axis different from an axis of the linear actuator, with such achange combining with the adjustment of the linear actuator to providethe change in native antenna pattern.

The feed array assembly may be operatively located between the reflectorsurface and the reflector focal region (e.g., in a defocused position).In some examples the actuator may provide an adjustment to the relativedistance between the reflector and the feed array assembly of acommunications satellite (e.g., using a linear actuator), which may, inturn, support operation at one of multiple native antenna patterns. Insome examples, following a change in relative position between the feedarray assembly and the reflector, a different beamforming weight set maybe applied as part of the second native antenna pattern (e.g., to adapta size and/or position of spot beam coverage areas, to adapt a degree ofoverlap amongst a plurality of spot beam coverage areas, to adapt a setof antenna feed elements of the feed array assembly used for one or moresatellite spot beams, etc.).

As used herein, the term “focal region” refers to the one, two, or threedimensional regions in front of a reflector (e.g., a spherical reflectoror a parabolic reflector) in which the reflector will reflectelectromagnetic energy received from a particular direction. For anideal parabolic reflector, the focal region is a single point in thehigh frequency limit scenario. This is often referred to as the“geometric optics” focal point for the ideal parabolic reflector. Inreal world implementations, the surfaces of even the most advancedreflectors include errors, distortions, and deviations from the profileof the deal surface. Uncorrelated errors, distortions, or deviations inthe surface of a reflector of any significant size may cause adistribution of focal points in a two or three dimensional focal region.Similarly, in the case of a spherical reflector, in which the idealsurface results in a line of focal points instead of single focal point,errors, distortions, or deviations in the surface of real worldspherical reflectors from the ideal spherical surface result in a threedimensional spread of the line focal region. In some embodiments, thefocal region associated with the reflector is determined based on raysthat are on-boresight, or parallel to the optical axis, of thereflector. In other embodiments, the focal region may be definedrelative to a reference direction that is off-boresight of thereflector. A system of two or more reflectors may also be fed by aphased array with the system having a focal region.

Operationally, positioning of a feed array assembly between the surfaceof a shaped reflector and a focal region of the shaped reflector (e.g.,the feed array assembly having a reference surface of antenna feedelement aperture openings located between the shaped reflector and thefocal region along a reference axis of the reflector, etc.) correspondsto a defocused position. Such an arrangement may result in a broadernative feed element pattern (e.g., broader native feed elementbeamwidth) than when the feed array assembly is positioned at the focalregion of the shaped reflector, which may improve versatility forforming beamformed spot beams using multiple native feed elementpatterns.

Various other configurations are possible for providing a change innative antenna pattern for providing a communications service. Forexample, an antenna assembly may include more than one reflector, andone or more actuators may be located between the feed array assembly andone of the reflectors, and/or between a first reflector and a secondreflector. In some examples a reflector may have its own actuator thatmay change the reflection characteristics of the reflector (e.g., changethe location of a focal region, change the focal region from aone-dimensional focal region to a two-dimensional region, change from asingle focal point to multiple focal points, change the shape of a focalregion, etc.). Additionally or alternatively, a feed array assembly mayinclude an actuator, which may provide a change in position and/ororientation for one or more feed elements of the feed array assembly(e.g., changing a feed array assembly from having feed element apertureson a planar surface to having feed element apertures on an arced orspherical surface, moving a subset of feed element apertures withrespect to another subset of feed element apertures, expanding orcontracting a pattern of feed elements, etc.). In various examples, anantenna assembly may include any combination of the described actuatorassemblies to provide various changes in native antenna pattern foradapting a communications service.

An actuator of a communications satellite may be commanded in variousways to provide an adjustment to the native antenna pattern of anantenna assembly. For example, a central controller or central operator(e.g., a communications service manager) may provide an indication ofthe adjustment to the communications satellite by way of wirelesssignaling received at the communications satellite. In some examples,the change may be commanded by a controller of the communicationssatellite itself. Commanding the adjustment to the actuator may includeproviding an indication of a new position of the actuator, a differencein relative distance between the reflector and the feed array assembly,a desired position of the reflector, a desired position of the feedarray assembly, a length of the actuator, a parameter of a new nativeantenna pattern, a lookup value associated with a new native antennapattern, or any other suitable parameter or indication.

In some examples commanding an adjustment to the native antenna patternmay be triggered by, or be otherwise based on an orbital position or achange in orbital position of the communications satellite (e.g., adeployed orbital position or path being different from a designedposition, a drift from a desired position or path over time, etc.). Insome examples, this flexibility may permit an antenna assembly to bedesigned without prior knowledge of a deployed orbital position, withoutprior knowledge of a desired service coverage area, and/or to bedesigned to support operation at a plurality of orbital positions orservice coverage areas. Accordingly, once deployed in a particularorbital position, such an antenna assembly may be commanded to provide anative antenna pattern that supports a communications service over adesired service coverage area according to the deployed orbitalposition. Additionally or alternatively the communications satellite maybe commanded to move to a different orbital position (e.g., a differentorbital slot) along with the command to adjust the native antennapattern, and provide the communications service from a new orbitalposition. In some examples commanding the adjustment to the nativeantenna pattern may be triggered based at least in part on various otherconditions, such as a level of communications traffic associated withthe communication service, relative levels of traffic between aplurality of beamformed spot beams, signal quality characteristics(e.g., signal strength, signal to noise ratio (SNR), signal tointerference plus noise ratio (SINR), signal quality characteristics ofa native feed element pattern, signal quality characteristics of a spotbeam, etc.), an outage or other failure of one of more antenna feedelements, an outage (e.g., loss of communications with), addition (e.g.,initiation of communications with), or other change in service of one ormore access node terminals, thermal expansion and/or other distortionthat changes a relative position between a feed array assembly and areflector, etc.

This description provides examples, and is not intended to limit thescope, applicability or configuration of embodiments of the principlesdescribed herein. Rather, the following description will provide thoseskilled in the art with an enabling description for implementingembodiments of the principles described herein. Various changes may bemade in the function and arrangement of elements.

Thus, various embodiments may omit, substitute, or add variousprocedures or components as appropriate. For instance, it should beappreciated that the methods may be performed in an order different thanthat described, and that various steps may be added, omitted orcombined. Also, aspects and elements described with respect to certainembodiments may be combined in various other embodiments. It should alsobe appreciated that the following systems, methods, devices, andsoftware may individually or collectively be components of a largersystem, wherein other procedures may take precedence over or otherwisemodify their application.

FIG. 1A shows a diagram of a satellite communications system 100 thatsupports flexible beamforming of satellite communications, in accordancewith aspects of the present disclosure. Satellite communications system100 may use a number of network architectures consisting of a spacesegment 101 and ground segment 102. The space segment may include one ormore communications satellites 120. The ground segment may include theone or more user terminals 150, one or more access node terminals 130(e.g., gateway terminals), as well as network devices 141 such asnetwork operations centers (NOCs), and satellite and gateway terminalcommand centers. The terminals of the satellite communications system100 (e.g., access node terminals 130) may be connected to each other,and/or to one or more networks 140, via a mesh network, a star network,or the like.

The communications satellite 120 may be any suitable type ofcommunications satellite configured for wireless communication with theone or more access node terminals 130 and the one or more user terminals150. In some examples the communications satellite 120 may be deployedin a geostationary orbit, such that its orbital position with respect toterrestrial devices is relatively fixed, or fixed within an operationaltolerance or other orbital window (e.g., within an orbital slot). Inother examples, the communications satellite 120 may operate in anyappropriate orbit (e.g., low Earth orbit (LEO), medium Earth orbit(MEO), etc.). In some examples the communications satellite 120 may havean uncertain orbital position, which may be associated with thecommunications satellite 120 being designed prior to determining anorbital slot deployment, being deployed to one of a range of possibleorbital positions (e.g., an orbital slot having a range of orbitalpositions, or being deployed to one of a set of orbital slots), a rangeof orbital paths, and/or drifting over time after deployment to anunintended orbital position and/or orbital path. In various examples thecommunications satellite 120 may be retasked (e.g., moved to a differentgeostationary orbital slot, adjusted to a different LEO or MEO orbitalpath, etc.), wherein such retasking may be commanded by thecommunications satellite 120 itself, and/or commanded by signalsreceived at the communications satellite 120 (e.g., from an access nodeterminal 130, from a network device 141, etc.).

Communications satellite 120 may use an antenna assembly 121, such as aphased array antenna assembly, a phased array fed reflector (PAFR)antenna, or any other mechanism known in the art for transmission and/orreception of signals of a communications service. Communicationssatellite 120 may receive forward uplink signals 132 from one or moreaccess node terminals 130 and provide corresponding forward downlinksignals 172 to one or more user terminals 150. Communications satellite120 may also receive return uplink signals 173 from one or more userterminals 150 and forward corresponding return downlink signals 133 toone or more access node terminals 130. A variety of physical layertransmission modulation and coding techniques may be used by thecommunications satellite 120 for the communication of signals betweenaccess node terminals 130 and user terminals 150 (e.g., adaptive codingand modulation(ACM), etc.).

In some embodiments, a Multi-Frequency Time-Division Multiple Access(MF-TDMA) scheme is used for forward uplink signals 132 and returnuplink signals 173, allowing efficient streaming of traffic whilemaintaining flexibility in allocating capacity among user terminals 150.In these embodiments, a number of frequency channels are allocated whichmay be fixed, or which may be allocated in a more dynamic fashion. ATime Division Multiple Access (TDMA) scheme may also be employed in eachfrequency channel. In this scheme, each frequency channel may be dividedinto several timeslots that can be assigned to a connection (e.g., to aparticular user terminal 150). In other embodiments, one or more of theforward uplink signals 132 and uplink return signals 173 may beconfigured using other schemes, such as Frequency Division MultipleAccess (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA),Code Division Multiple Access (CDMA), or any number of hybrid or otherschemes known in the art. In various embodiments, physical layertechniques may be the same for each of the signals 132, 133, 172, and173, or some of the signals may use different physical layer techniquesthan other signals.

The antenna assembly 121 may support communication via one or morebeamformed spot beams 125, which may be otherwise referred to as servicebeams, satellite beams, or any other suitable terminology. Signals maybe passed via the antenna assembly 121 to form the spatialelectromagnetic radiation pattern of the spot beams 125. A spot beam 125may use a single carrier, i.e., one frequency or a contiguous frequencyrange, per spot beam. In some examples, a spot beam 125 may beconfigured to support only user terminals 150, in which case the spotbeam 125 may be referred to as a user spot beam or a user beam (e.g.,user spot beam 125-a). For example, a user spot beam 125-a may beconfigured to support one or more forward downlink signals 172 and/orone or more return uplink signals 173 between the communicationssatellite 120 and user terminals 150. In some examples, a spot beam 125may be configured to support only access node terminals 130, in whichcase the spot beam 125 may be referred to as an access node spot beam,an access node beam, or a gateway beam (e.g., access node spot beam125-b). For example, an access node spot beam 125-b may be configured tosupport one or more forward uplink signals 132 and/or one or more returndownlink signals 133 between the communications satellite 120 and accessnode terminals 130. In other examples, a spot beam 125 may be configuredto service both user terminals 150 and access node terminals 130, andthus a spot beam 125 may support any combination of forward downlinksignals 172, return uplink signals 173, forward uplink signals 132,and/or return downlink signals 133 between the communications satellite120 and user terminals 150 and access node terminals 130.

A spot beam 125 may support the communications service between targetdevices (e.g., user terminals 150 and/or access node terminals 130)within a spot beam coverage area 126. A spot beam coverage area 126 maybe defined by an area of the electromagnetic radiation pattern of theassociated spot beam 125, as projected on the ground or some otherreference surface, having a signal power (e.g., SNR, SINR, etc.) of spotbeam 125 above a threshold. A spot beam coverage area 126 may cover anysuitable service area (e.g., circular, elliptical, hexagonal, local,regional, national, etc.) and may support a communications service withany number of target devices located in the spot beam coverage area 126(which may include target devices located within the associated spotbeam 125, but not necessarily at the reference surface of a spot beamcoverage area 126, such as airborne or underwater terminals).

In some examples the communications satellite 120 may support multiplebeamformed spot beams 125 covering respective spot beam coverage areas126, each of which may or may not overlap with adjacent spot beamcoverage areas 126. For example, the communications satellite 120 maysupport a service coverage area (e.g., a regional coverage area, anational coverage area, etc.) formed by the combination of any number(e.g., tens, hundreds, thousands, etc.) of spot beam coverage areas 126.The communications satellite 120 may support a communications service byway of one or more frequency bands, and any number of subbands thereof.For example, the communications satellite 120 may support operations inthe International Telecommunications Union (ITU) Ku, K, or Ka-bands,C-band, X-band, S-band, L-band, V-band, and the like.

A service coverage area may be broadly defined as a coverage area fromwhich, and/or to which, either a terrestrial transmission source, or aterrestrial receiver may be participate in (e.g., transmit and/orreceive signals associated with) a communications service via thecommunications satellite 120, and may be defined by a plurality of spotbeam coverage areas 126. In some systems, the service coverage area foreach communications link (e.g., a forward uplink coverage area, aforward downlink coverage area, a return uplink coverage area, and/or areturn downlink coverage area) may be different. While the servicecoverage area may only be active when the communications satellite 120is in service (e.g., in a service orbit), the communications satellite120 may have (e.g., be designed to have) a native antenna pattern thatis based on the physical components of the antenna assembly 121, andtheir relative positions, for example. A native antenna pattern of thecommunications satellite 120 may refer to a distribution of energy withrespect to an antenna assembly 121 of a satellite (e.g., energytransmitted from and/or received by the antenna assembly 121).

In some service coverage areas, adjacent spot beam coverage areas 126may have some degree of overlap. In some examples, a multi-color (e.g.,two, three or four-color re-use pattern) may be used, wherein a “color”refers to a combination of orthogonal communications resources (e.g.,frequency resources, polarization, etc.). In an example of a four-colorpattern, a number of overlapping spot beam coverage areas 126 may eachbe assigned with one of the four colors, and each color may be allocateda unique combination of frequency (e.g., a frequency range or ranges,one or more channels, etc.) and/or signal polarization (e.g., aright-hand circular polarization (RHCP), a left-hand circularpolarization (LHCP), etc.). By assigning different colors to respectivespot beam coverage areas 126 that have overlapping regions, there may berelatively little mutual interference between the spot beams 125associated with those overlapping spot beam coverage areas 126. Thesecombinations of frequency and antenna polarization may accordingly bere-used in the repeating non-overlapping “four-color” re-use pattern. Insome examples, a desired communication service may be provided by usingmore or fewer colors. Additionally or alternatively, time sharing amongspot beams 125 and/or other interference mitigation techniques may beused. For example, spot beams 125 may concurrently use the sameresources (the same polarization and frequency range) with interferencemitigated using interference mitigation techniques such as ACM,interference cancellation, space-time coding, and the like.

In some examples the communications satellite 120 may be configured as a“bent pipe” satellite. In a bent pipe configuration, communicationssatellite 120 may perform frequency and polarization conversion of thereceived carrier signals before re-transmission of the signals to theirdestination. In some examples the communications satellite 120 maysupport a non-processed bent pipe architecture, with phased arrayantennas used to produce small spot beams 125 (e.g., by way ofground-based beamforming (GBBF)). The communications satellite 120 maycontain K generic pathways, each of which can be allocated as a forwardpathway or a return pathway at any instant of time. Large reflectors maybe illuminated by a phased array of antenna feed elements, providing theability to make various patterns of spot beams 125 within theconstraints set by the size of the reflector and the number andplacement of the antenna feed elements. Phased array fed reflectors maybe employed for both receiving uplink signals 132, 173, or both, andtransmitting downlink signals 133, 172, or both.

Communications satellite 120 may operate in a multiple spot beam mode,transmitting a number of narrow spot beams 125 directed at differentregions of the earth. This may allow for segregation of user terminals150 into the various narrow spot beams 125. Beamforming networks (BFNs)associated with the receive (Rx) and transmit (Tx) phased arrays may bedynamic, allowing for frequent movement of the locations of both the Txspot beams 125 (e.g., downlink spot beams 125) and Rx spot beams 125(e.g., uplink spot beams 125). The dynamic BFNs may be used to quicklyhop the positions of both Tx and Rx spot beams 125. The BFN may dwell inone beam hopping pattern (e.g., both Tx and Rx spot beams 125) for aperiod of time called a timeslot dwell time. Individual timeslots mayall be associated with the same dwell time or different dwell times. Anumber Q of these timeslots, with each timeslot associated with apotentially different location pattern of Rx and Tx spot beams, arearranged into a sequence called a beam hopping frame. These frames canrepeat, but may also be dynamic and time-varying. The duration andlocation of the Rx and Tx spot beams associated with beam hop timeslotscan also vary, both between frames and within a frame.

User terminals 150 may include any number of devices configured tocommunicate signals with the communications satellite 120, which mayinclude fixed terminals (e.g., ground-based stationary terminals) ormobile terminals such as terminals on boats, aircraft, ground-basedvehicles, and the like. A user terminal 150 may communicate data andinformation via the communications satellite 120, which may includecommunications via an access node terminal 130 to a destination devicesuch as a network device 141, or some other device or distributed serverassociated with a network 140. A user terminal 150 may communicatesignals according to a variety of physical layer transmission modulationand coding techniques, including, for example, those defined with theDVB-S2, WiMAX, LTE, and DOCSIS standards.

A user terminal 150 may include a user terminal antenna 152 configuredfor receiving forward downlink signals 172 from the communicationssatellite 120. The user terminal antenna 152 may also be configured totransmit return uplink signals 173 to the communications satellite 120.Thus, a user terminal 150 may be configured for uni-directional orbi-directional communications with the communications satellite 120 viaa spot beam 125 (e.g., user spot beam 125-a). In some examples the userterminal antenna 152 may be directional. For example, the user terminalantenna 152 may have a peak gain along a primary axis (e.g., an antennaboresight direction), which may be provided by way of a fixedconfiguration of focusing and/or reflecting elements, and/or by way ofelectronically configurable beamforming.

A user terminal antenna 152 may be part of a user terminal antennaassembly 153, which may also include various hardware for mounting thesatellite terminal antennas. A user terminal antenna assembly 153 mayalso include circuits and/or processors for converting (e.g., performingfrequency conversion, modulating/demodulating,multiplexing/demultiplexing, filtering, forwarding, etc.) between radiofrequency (RF) satellite communication signals (e.g., forward downlinksignals 172 and/or return uplink signals 173), and user terminalcommunications signals 157 transmitted between the user terminal antenna152 and a user terminal receiver 158. Such circuits and/or processorsmay be included in an antenna communication assembly, which may also bereferred to as a transmit and receive integrated assembly (TRIA).Additionally or alternatively, the user terminal receiver 158 mayinclude circuits and/or processors for performing various RF signaloperations (e.g., receiving, performing frequency conversion,modulating/demodulating, multiplexing/demultiplexing, etc.). The userterminal antenna assembly 153 may also be known as a satellite outdoorunit (ODU), and the user terminal receiver 158 may be known as asatellite indoor unit (IDU). In some examples, the user terminal antenna152 and user terminal receiver 158 together comprise a very smallaperture terminal (VSAT), with user terminal antenna 152 measuringapproximately 0.6 meters in diameter and having approximately 2 watts ofpower. In other embodiments, a variety of other types of user terminalantennas 152 may be used at user terminals 150 to receive forwarddownlink signals 172 from the communications satellite 120. Each of userterminals 150 may comprise a single user terminal or, alternatively, maycomprise a hub or router (not shown) that is coupled to multiple userterminals 150.

A user terminal 150 may be connected via a wired or wireless connection161 to one or more consumer premises equipment (CPE) 160 and may providenetwork access service (e.g., Internet access, etc.) or othercommunication services (e.g., broadcast media, etc.) to CPEs 160 via thesatellite communications system. The CPE(s) 160 may include user devicessuch as, but not limited to, computers, local area networks, internetappliances, wireless networks, mobile phones, personal digitalassistants (PDAs), other handheld devices, netbooks, notebook computers,tablet computers, laptops, display devices (e.g., TVs, computermonitors, etc.), printers, and the like. The CPE(s) 160 may also includeany equipment located at a premises of a subscriber, including routers,firewalls, switches, private branch exchanges (PBXs), Voice overInternet Protocol (VoIP) gateways, and the like. In some examples, theuser terminal 150 provides for two-way communications between the CPE(s)160 and network(s) 140 via the communications satellite 120 and theaccess node terminal(s) 130.

An access node terminal 130 may service forward uplink signals 132 andreturn downlink signals 133 to and from communications satellite 120.Access node terminals 130 may also be known as ground stations,gateways, gateway terminals, or hubs. An access node terminal 130 mayinclude an access node terminal antenna system 131 and an access nodereceiver 135. The access node terminal antenna system 131 may be two-waycapable and designed with adequate transmit power and receivesensitivity to communicate reliably with the communications satellite120. In one embodiment, access node terminal antenna system 131 maycomprise a parabolic reflector with high directivity in the direction ofa communications satellite 120 and low directivity in other directions.Access node terminal antenna system 131 may comprise a variety ofalternative configurations and include operating features such as highisolation between orthogonal polarizations, high efficiency in theoperational frequency bands, low noise, and the like.

An access node terminal 130 may schedule traffic to user terminals 150.Alternatively, the scheduling may be performed in other parts ofsatellite communications system 100 (e.g., at one or more networkdevices 141, which may include network operations centers (NOC) and/orgateway command centers). Although only one access node terminal 130 isshown in FIG. 1A, embodiments of the present invention may beimplemented in satellite communications systems having a plurality ofaccess node terminals 130, each of which may be coupled to each otherand/or one or more networks 140.

In some satellite communications systems, there may be a limited amountof frequency spectrum available for transmission. Communication linksbetween access node terminals 130 and the communications satellite 120may use the same, overlapping, or different frequencies as communicationlinks between communications satellite 120 and user terminals 150.Access node terminals 130 may also be located remotely from userterminals 150 to facilitate frequency re-use.

The communications satellite 120 may communicate with an access nodeterminal 130 by transmitting return downlink signals 133 and/orreceiving forward uplink signals 132 via one or more spot beams 125(e.g., access node spot beam 125-b, which may be associated with arespective access node spot beam coverage area 126-b). Access node spotbeam 125-b may, for example, support a communications service for one ormore user terminals 150 (e.g., relayed by the communications satellite120), or any other communications between the communications satellite120 and the access node terminal 130.

Access node terminal 130 may provide an interface between the network140 and the communications satellite 120, and may be configured toreceive data and information directed between the network 140 and one ormore user terminals 150. Access node terminal 130 may format the dataand information for delivery to respective user terminals 150.Similarly, access node terminal 130 may be configured to receive signalsfrom the communications satellite 120 (e.g., from one or more userterminals 150) directed to a destination accessible via network 140.Access node terminal 130 may also format the received signals fortransmission on network 140.

The network(s) 140 may be any type of network and can include, forexample, the Internet, an IP network, an intranet, a wide-area network(WAN), a metropolitan area network (MAN), a local-area network (LAN), avirtual private network (VPN), a virtual LAN (VLAN), a fiber opticnetwork, a hybrid fiber-coax network, a cable network, a public switchedtelephone network (PSTN), a public switched data network (PSDN), apublic land mobile network, and/or any other type of network supportingcommunications between devices as described herein. Network(s) 140 mayinclude both wired and wireless connections as well as optical links.Network(s) 140 may connect the access node terminal 130 with otheraccess node terminals that may be in communication with thecommunications satellite 120 or with other satellites.

One or more network device(s) 141 may be coupled with the access nodeterminal 130 and may control aspects of the satellite communicationssystem 100. In various examples a network device 141 may be co-locatedor otherwise nearby the access node terminal 130, or may be a remoteinstallation that communicates with the access node terminal 130 and/ornetwork(s) 140 via wired and/or wireless communications link(s).

FIG. 1B illustrates an antenna assembly 121 of a communicationssatellite 120 that supports flexible beamforming of satellitecommunications, in accordance with aspects of the present disclosure. Asshown in FIG. 1B, the antenna assembly 121 may include a feed arrayassembly 127 and a reflector 122 that is shaped to have a focal region123 where electromagnetic signals (e.g., inbound electromagnetic signals180) are concentrated when received from a distant source. Similarly, asignal emitted by a feed array assembly 127 located at the focal region123 will be reflected by reflector 122 into an outgoing plane wave(e.g., outbound electromagnetic signals 180). The feed array assembly127 and the reflector 122 may be associated with a native antennapattern formed by the composite of native feed element patterns for eachof a plurality of feed elements 128 of the feed array assembly 127.

A communications satellite 120 may operate according to native antennapattern of the antenna assembly 121 when the communications satellite120 is in a service orbit, as described herein. The native antennapattern may be based at least in part on a pattern of feed elements 128of a feed array assembly 127, a relative position (e.g., a focal offsetdistance 129) of a feed array assembly 127 with respect to a reflector122, etc. The native antenna pattern 220 may be associated with a nativeantenna pattern coverage area. Antenna assemblies 121 described hereinmay be designed to support a particular service coverage area with thenative antenna pattern coverage area of an antenna assembly 121, andvarious design characteristics may be determined computationally (e.g.,by analysis or simulation) and/or measured experimentally (e.g., on anantenna test range or in actual use).

As shown in FIG. 1B, the feed array assembly 127 of the antenna assembly121 is located between the reflector 122 and the focal region 123 of thereflector 122. Specifically, the feed array assembly 127 is located at afocal offset distance 129 from the focal region 123. Accordingly, thefeed array assembly 127 of the antenna assembly 121 may be located at adefocused position with respect to the reflector 122. The antennaassembly 121 may also include an actuator 124, which may provide for achange in native antenna pattern as described herein. For example, theactuator 124 may be a linear actuator coupled between the reflector 122and the feed array assembly 127, which provides a change to the focaloffset distance 129 to provide the change in native antenna pattern. Alinear actuator 124 may be constrained to move in one direction, whichin some examples may be aligned along a direction predominantly betweena center of the shaped reflector 122 and the focal region 123 of theshaped reflector 122. Although illustrated in FIG. 1B as a direct offsetfeed array assembly 127, a front feed array assembly 127 may be used, aswell as other types of configurations, including the use of a secondaryreflector (e.g., Cassegrain antenna, etc.).

FIG. 1C illustrates a feed array assembly 127 of an antenna assembly 121that supports flexible beamforming of satellite communications, inaccordance with aspects of the present disclosure. As shown in FIG. 1C,the feed array assembly 127 may have multiple antenna feed elements 128for communicating signals (e.g., signals associated with acommunications service, signals associated with a configuration orcontrol of the communications satellite 120, etc.).

As used herein, a feed element 128 may refer to a receive antennaelement, a transmit antenna element, or an antenna element configured tosupport both transmitting and receiving (e.g., a transceiver element). Areceive antenna element may include a physical transducer (or RFtransducer) that converts an electromagnetic signal to an electricalsignal, and the term transmit antenna element may refer to an elementincluding a physical transducer that emits an electromagnetic signalwhen excited by an electrical signal. The same physical transducer maybe used for transmitting and receiving, in some cases.

Each of the feed elements 128 may include, for example, a feed horn, apolarization transducer (e.g., a septum polarized horn, which mayfunction as two combined elements with different polarizations), amulti-port multi-band horn (e.g., dual-band 20 GHz/30 GHz with dualpolarization LHCP/RHCP), a cavity-backed slot, an inverted-F, a slottedwaveguide, a Vivaldi, a Helical, a loop, a patch, or any otherconfiguration of an antenna element or combination of interconnectedsub-elements. Each of the feed elements 128 may also include, or beotherwise coupled with an RF signal transducer, a low noise amplifier(LNA), or power amplifier (PA), and may be coupled with transponders inthe communications satellite 120 that may perform other signalprocessing such as frequency conversion, beamforming processing, and thelike.

The reflector 122 may be configured to reflect the signals transmittedbetween the feed array assembly 127 and one or more target devices(e.g., user terminals 150, access node terminals 130, etc.). Each feedelement 128 of the feed array assembly 127 may be associated with arespective native feed element pattern, which may be further associatedwith a projected native feed element pattern coverage area (e.g., asprojected on a terrestrial surface, plane, or volume after reflectionfrom the reflector 122). The collection of the native feed elementpattern coverage areas for a multi-feed antenna may be referred to as anative antenna pattern. The feed array assembly 127 may include anynumber of feed elements 128 (e.g., tens, hundreds, thousands, etc.),which may be arranged in any suitable arrangement (e.g., a linear array,an arcuate array, a planar array, a honeycomb array, a polyhedral array,a spherical array, an ellipsoidal array, or combinations thereof).Although each feed element 128 is shown in FIG. 1C as circular, feedelements 128 may be other shapes such as square, rectangular, hexagonal,and others.

FIGS. 2A through 2D illustrate examples of antenna characteristics foran antenna assembly 121-a having a feed array assembly 127-a located ata focal region 123 of a shaped reflector 122-a, in accordance withaspects of the present disclosure.

FIG. 2A shows a diagram 201 of native feed element patterns 210-aassociated with feed elements 128-a of the feed array assembly 127-a.Specifically, diagram 201 illustrates native feed element patterns210-a-1, 210-a-2, and 210-a-3, associated with feed elements 128-a-1,128-a-2, and 128-a-3, respectively. The native feed element patterns210-a may represent the spatial radiation pattern associated with eachof the respective feed elements 128. For example, when feed element128-a-2 is transmitting, transmitted electromagnetic signals may bereflected off the reflector 122-a, and propagate in a generally conicalnative feed element pattern 210-a-2 (although other shapes are possibledepending on the characteristics of a feed element 128 and/or reflector122). Although only three native feed element patterns 210-a are shownfor the antenna assembly 121-a, each of the feed elements 128 of anantenna assembly 121 is associated with a respective native feed elementpattern 210. The composite of the native feed element patterns 210-aassociated with the antenna assembly 121-a (e.g., native feed elementpatterns 210-a-1, 210-a-2, 210-a-2, and other native feed elementpatterns 210-a that are not illustrated) may be referred to as thenative antenna pattern 220-a.

Each of the feed elements 128-a may also be associated with a nativefeed element pattern coverage area 211-a (e.g., native feed elementpattern coverage areas 211-a-1, 211-a-2, and 211-a-3, associated withfeed elements 128-a-1, 128-a-2, and 128-a-3, respectively), representingthe projection of the native feed element patterns 210-a on a referencesurface (e.g., the ground, or some other reference plane or surface). Anative feed element pattern coverage area 211 may represent an area inwhich various devices (e.g., access node terminals 130 and/or userterminals 150) may receive signals transmitted by a respective feedelement 128. Additionally or alternatively, a native feed elementpattern coverage area 211 may represent an area in which transmissionsfrom various devices may be received by a respective feed element 128.For example, a device located at an area of interest 230-a, locatedwithin the native feed element pattern coverage area 211-a-2 may receivesignals transmitted by feed element 128-a-2, and may have transmissionsreceived by feed element 128-a-2. The composite of the native feedelement pattern coverage areas 211-a associated with the antennaassembly 121-a (e.g., native feed element pattern coverage areas211-a-1, 211-a-2, 211-a-2, and other native feed element patterncoverage areas 211-a that are not illustrated) may be referred to as thenative antenna pattern coverage area 221-a. It should be understood thatdiagram 201 is not drawn to scale and that native feed element patterncoverage areas 211 are generally each much larger than the reflector122-a. Because the feed array assembly 127-a is located at a focalregion 123 of the reflector 122-a, the native feed element patterns210-a are substantially non-overlapping in the region of the nativeantenna pattern coverage area 221-a, and thus the native feed elementpattern coverage areas 211-a, are substantially non-overlapping.Therefore each position in the native antenna pattern coverage area221-a is associated with one or a small number (e.g., 3 or fewer) offeed elements 128.

FIG. 2B shows a diagram 202 illustrating signal reception of the antennaassembly 121-a for transmissions 240 a from the point of interest 230 a.Transmissions 240 a from the point of interest 230 a may illuminate theentire reflector 122-a, or some portion of the reflector 122-a, and thenbe focused and directed towards the feed array assembly 127-a accordingto the shape of the reflector 122-a and the angle of incidence of thetransmission 240 on the reflector 122-a. Because the feed array assembly127-a is located at a focal region 123 of the reflector 122-a, thetransmissions 240 a may be focused to a single feed element (e.g., feedelement 128-a-2, associated with the native feed element patterncoverage area 211-a-2 in which the point of interest 230 a is located),or, if located in an area of overlap of the native feed element patterncoverage areas 211-a, a small number (e.g., 3 or fewer) of feed elements128-a.

FIG. 2C shows a diagram 203 of native feed element pattern gain profiles250-a associated with three antenna feed elements 128-a of the feedarray assembly 127-a, with reference to angles measured from a zerooffset angle 235-a. For example, native feed element pattern gainprofiles 250-a-1, 250-a-2, and 250-a-3 may be associated with antennafeed elements 128-a-1, 128-a-2, and 128-a-3, respectively, and thereforemay represent the gain profiles of native feed element patterns 210-a-1,210-a-2, and 210-a-3. As shown in diagram 203, the gain of each nativefeed element pattern gain profile 250 may attenuate at angles offset ineither direction from the peak gain. In diagram 203, beam contour level255-a may represent a desired gain level (e.g., to provide a desiredinformation rate, etc.) to support a communications service via theantenna assembly 121-a, which therefore may be used to define a boundaryof respective native feed element pattern coverage areas 211-a (e.g.,native feed element pattern coverage areas 211-a-1, 211-a-2, and211-a-3). Beam contour level 255-a may represent, for example, a −1 dB,−2 dB, or −3 dB attenuation from the peak gain, or may be defined by anabsolute signal strength, SNR, or SINR level. Although only three nativefeed element pattern gain profiles 250 a are shown, other native feedelement pattern gain profiles 250 a may be associated with other antennafeed elements 128-a.

FIG. 2D shows a diagram 204 illustrating a two-dimensional array ofidealized native feed element pattern coverage areas 211 of several feedelements 128 of the feed array assembly 127-a (e.g., including feedelements 128-a-1, 128-a-2, and 128-a-3). The native feed element patterncoverage areas 211 may be illustrated with respect to reference surface(e.g., a plane at a distance from the communications satellite, a planeat some distance from the ground, a spherical surface at some elevation,a ground surface, etc.), and may additionally include a volume adjacentto the reference surface (e.g., a substantially conical volume betweenthe reference surface and the communications satellite, a volume belowthe reference surface, etc.). The multiple native feed element patterncoverage areas 211-a may collectively form the native antenna patterncoverage area 221-a. Although only eight native feed element patterncoverage areas 211-a are illustrated, a feed array assembly 127 may haveany number of feed elements 128 (e.g., fewer than eight or more thaneight), each associated with a native feed element pattern coverage area211.

The boundaries of each native feed element pattern coverage area 211 maycorrespond to the respective native feed element pattern 210 at the beamcontour level 255-a, and the peak gain of each native feed elementpattern coverage area 211 may have a location designated with an ‘x.’Native feed element pattern coverage areas 211-a-1, 211-a-2, and 211-a-3may correspond to the projection of the native feed element patternsassociated with native feed element pattern gain profiles 250-a-1,250-a-2, and 250-a-3, respectively, where diagram 203 illustrates thenative feed element pattern gain profiles 250 along section plane 260 aof diagram 204. In diagram 204, because the feed array assembly 127-a islocated at a focal region of the reflector 122-a, only a relativelysmall portion of each native feed element pattern coverage area 211overlaps with an adjacent native feed element pattern coverage area 211.In addition, generally locations within a service coverage area (e.g., atotal coverage area of a plurality of spot beams of a communicationssatellite) fall within the native feed element pattern coverage area 211of two or fewer antenna feed elements 128. For example, the antennaassembly 121-a may be configured such that the area where more than twonative feed element pattern coverage areas 211 overlap is minimized(e.g., three native feed element pattern coverage areas 211 may beconfigured to intersect at or close to a point as shown in FIG. 2D,etc.). In some examples, this condition may also be referred to ashaving feed elements 128 of a feed array assembly 127, or native feedelement pattern coverage areas 211, being tiled. The native feed elementpattern coverage areas 211 are referred to herein as idealized becausethe coverage areas are shown as circular for the sake of simplicity.However, in various examples a native feed element pattern coverage area211 may be some shape other than a circle (e.g., an ellipse, a hexagon,a rectangle, etc.). Thus, tiled native feed element pattern coverageareas 211 may have more overlap with each other (e.g., more than threenative feed element pattern coverage areas 211 may overlap, in somecases) than shown in diagram 204.

FIGS. 3A through 3D illustrate examples of antenna characteristics foran antenna assembly 121-b having a feed array assembly 127-b operatingin a defocused position, in accordance with aspects of the presentdisclosure. When feed array assembly 127-b is not located at a focalregion 123 of an antenna assembly 121, the antenna assembly 121 may beunderstood as operating in a defocused condition. In a defocusedcondition, an antenna assembly 121 spreads received transmissions from agiven location to more of the antenna feed elements 128, and spreadstransmitted power from a feed element 128 over a larger area. Thus, eachnative feed element pattern 210 has a larger beamwidth, and there is alarger amount of overlap between native feed element patterns 210.According to the example of FIGS. 3A through 3D, the defocused conditionmay be provided by locating the feed array assembly 127-b between thereflector 122-b and a focal region 123 of the reflector 122-b (e.g.,offset by focal offset distance 129) as shown in FIG. 1B.

FIG. 3A shows a diagram 301 of native feed element patterns 210-bassociated with feed elements 128-b of the feed array assembly 127-b.Specifically, diagram 301 illustrates native feed element patterns210-b-1, 210-b-2, and 210-b-3, associated with feed elements 128-b-1,128-b-2, and 128-b-3, respectively. Although only three native feedelement patterns 210-b are shown for the antenna assembly 121-b, each ofthe feed elements 128 of an antenna assembly 121 is associated with arespective native feed element pattern 210. The composite of the nativefeed element patterns 210-b associated with the antenna assembly 121-b(e.g., native feed element patterns 210-b-1, 210-b-2, 210-b-2, and othernative feed element patterns 210-b that are not illustrated) may bereferred to as the native antenna pattern 220-b.

Each of the feed elements 128-b may also be associated with a nativefeed element pattern coverage area 211-b (e.g., native feed elementpattern coverage areas 211-b-1, 211-b-2, and 211-b-3, associated withfeed elements 128-b-1, 128-b-2, and 128-b-3, respectively), representingthe projection of the native feed element patterns 210-b on a referencesurface (e.g., the ground, or some other reference plane or surface).The composite of the native feed element pattern coverage areas 211-bassociated with the antenna assembly 121-b (e.g., native feed elementpattern coverage areas 211-b-1, 211-b-2, 211-b-2, and other native feedelement pattern coverage areas 211-b that are not illustrated) may bereferred to as the native antenna pattern coverage area 221-b. Becausethe feed array assembly 127-b is operating at a defocused position withrespect to the reflector 122-b, the native feed element patterns 210-b,and thus the native feed element pattern coverage areas 211-b, aresubstantially overlapping. Therefore each position in the native antennapattern coverage area 221-b may be associated with a plurality of feedelements 128.

FIG. 3B shows a diagram 302 illustrating signal reception of the antennaassembly 121-b for transmissions 240-b from a point of interest 230-b.Transmissions 240-b from the point of interest 230-b may illuminate theentire reflector 122-b, or some portion of the reflector 122-b, and thenbe focused and directed towards the feed array assembly 127-b accordingto the shape of the reflector 122-b and the angle of incidence of thetransmission 240 on the reflector 122-b. Because the feed array assembly127-b is operating at a defocused position with respect to the reflector122-b, the transmissions 240-b may be focused on a plurality of feedelements 128 (e.g., feed elements 128-b-1, 128-b-2, and 128-b-3,associated with the native feed element pattern coverage areas 211-b-1,211-b-2, and 211-b-3, each of which contain the point of interest230-b).

FIG. 3C shows a diagram 303 of native feed element pattern gain profiles250-b associated with three antenna feed elements 128-b of the feedarray assembly 127-b, with reference to angles measured from a zerooffset angle 235-b. For example, native feed element pattern gainprofiles 250-b-1, 250-b-2, and 250-b-3 may be associated with antennafeed elements 128-b-1, 128-b-2, and 128-b-3, respectively, and thereforemay represent the gain profiles of native feed element patterns 210-b-1,210-b-2, and 210-b-3. As shown in diagram 303, the gain of each nativefeed element pattern gain profile 250-b may attenuate at angles offsetin either direction from the peak gain. In diagram 303, beam contourlevel 255-b may represent a desired gain level (e.g., to provide adesired information rate, etc.) to support a communications service viathe antenna assembly 121-b, which therefore may be used to define aboundary of respective native feed element pattern coverage areas 211-b(e.g., native feed element pattern coverage areas 211-b-1, 211-b-2, and211-b-3). Beam contour level 255-b may represent, for example, a −1 dB,−2 dB, or −3 dB attenuation from the peak gain, or may be defined by anabsolute signal strength, SNR, or SINR level. Although only three nativefeed element pattern gain profiles 250-b are shown, other native feedelement pattern gain profiles 250-b may be associated with other antennafeed elements 128-b.

As shown in diagram 303, each of the native feed element pattern gainprofiles 250-b may intersect with another native feed element patterngain profile 250-b for a substantial portion of the gain profile abovethe beam contour level 255-b. Accordingly, diagram 303 illustrates anarrangement of native feed element pattern gain profiles 250 wheremultiple antenna feed elements 128 of a feed array assembly 127 maysupport a communications service at a particular angle (e.g., at aparticular direction of the native antenna pattern 220-b). In someexamples, this condition may be referred to as having feed elements 128of a feed array assembly 127, or native feed element pattern coverageareas 211, having a high degree of overlap.

FIG. 3D shows a diagram 304 illustrating a two-dimensional array ofidealized native feed element pattern coverage areas 211 of several feedelements 128 of the feed array assembly 127-b (e.g., including feedelements 128-b-1, 128-b-2, and 128-b-3). The native feed element patterncoverage areas 211 may be illustrated with respect to reference surface(e.g., a plane at a distance from the communications satellite, a planeat some distance from the ground, a spherical surface at some elevation,a ground surface, etc.), and may additionally include a volume adjacentto the reference surface (e.g., a substantially conical volume betweenthe reference surface and the communications satellite, a volume belowthe reference surface, etc.). The multiple native feed element patterncoverage areas 211-b may collectively form the native antenna patterncoverage area 221-b. Although only eight native feed element patterncoverage areas 211-b are illustrated, a feed array assembly 127 may haveany number of feed elements 128 (e.g., fewer than eight or more thaneight), each associated with a native feed element pattern coverage area211.

The boundaries of each native feed element pattern coverage area 211 maycorrespond to the respective native feed element pattern 210 at the beamcontour level 255-b, and the peak gain of each native feed elementpattern coverage area 211 may have a location designated with an ‘x.’Native feed element pattern coverage areas 211-b-1, 211-b-2, and 211-b-3may correspond to the projection of the native feed element patternsassociated with native feed element pattern gain profiles 250-b-1,250-b-2, and 250-b-3, respectively, where diagram 303 illustrates thebeam gain profiles along section plane 260-b of diagram 304. In diagram304, because the feed array assembly 127-a is located at a defocusedposition with respect to the reflector 122-b, a substantial portion(e.g., a majority) of each native feed element pattern coverage area 211overlaps with an adjacent native feed element pattern coverage area 211.In addition, generally locations within a service coverage area (e.g., atotal coverage area of a plurality of spot beams of a communicationssatellite) fall within the native feed element pattern coverage area 211of two or more antenna feed elements 128. For example, the antennaassembly 121-b may be configured such that the area where more than twonative feed element pattern coverage areas 211 overlap is maximized. Insome examples, this condition may also be referred to as having feedelements 128 of a feed array assembly 127, or native feed elementpattern coverage areas 211, having a high degree of overlap. Althoughonly eight native feed element pattern coverage areas 211 areillustrated, a feed array assembly 127 may have any number of antennafeed elements 128, associated with native feed element pattern coverageareas 211 in a like manner.

In some cases, for a feed array assembly 127 operating at a defocusedposition, a substantial amount (e.g., more than half) of a servicecoverage area (e.g., a total coverage area of a plurality of spot beamsof a communications satellite) falls within the boundaries of nativefeed element pattern coverage areas 211 of several (e.g., more than 2 ormore than 3) antenna feed elements 128. In one such case, at least onepoint is within the boundaries of at least 50% of the native feedelement pattern coverage areas 211 of the feed array assembly 127. Inanother case, at least 10 percent of a service coverage area lies withinthe boundaries of at least 25% of the native feed element patterncoverage areas 211. In another case, at least 20% of a service coveragearea lies within the boundaries of at least 20% of the native feedelement pattern coverage areas 211. In another case, at least 30% of theservice coverage area lies within the boundaries of at least 10% of thenative feed element pattern coverage areas 211. In another case, atleast 50% of the service coverage area lies within the boundaries of atleast 4 different native feed element pattern coverage areas 211. Forexample, for a service coverage area of 100 square miles and 200 feedelements 128, at least one point may be within 100 native feed elementpattern coverage areas 211, at least 10 square miles may be within 50native feed element pattern coverage areas 211, at least 20 square milesmay be within 40 native feed element pattern coverage areas 211, atleast 30 square miles may be within 20 native feed element patterncoverage areas 211, or at least 50 square miles may be within 4 or moreof the native feed element pattern coverage areas 211. However, in somecases, more than one of these relationships may be true.

In some cases, a single antenna assembly 121 may be used fortransmitting and receiving signals between user terminals 150 or accessnode terminals 130. In other examples, a communications satellite 120may include separate antenna assemblies 121 for receiving signals andtransmitting signals. A receive antenna assembly 121 of a communicationssatellite 120 may be pointed generally at the same service coverage areaas a transmit antenna assembly 121 of the communications satellite 120.Thus, some native feed element pattern coverage areas 211 for antennafeed elements 128 configured for reception may naturally correspond tonative feed element pattern coverage areas 211 for antenna feed elements128 configured for transmission. In these cases, the receive antennafeed elements 128 may be mapped in a manner similar to theircorresponding transmit antenna feed elements 128 (e.g., with similararray patterns of different feed array assemblies 127, with similarwiring and/or circuit connections to signal processing hardware, similarsoftware configurations and/or algorithms, etc.), yielding similarsignal paths and processing for transmit and receive native feed elementpattern coverage areas 211. In some cases, however, it may beadvantageous to map receive antenna feed elements 128 and transmitantenna feed elements 128 in dissimilar manners.

In some examples, a plurality of native feed element patterns 210 with ahigh degree of overlap may be combined by way of beamforming to provideone or more spot beams 125. Beamforming for a spot beam 125 may beperformed by adjusting the signal phase (or time delay) and/or signalamplitude, of signals transmitted and/or received by multiple feedelements 128 of one or more feed array assemblies 127 having overlappingnative feed element pattern coverage areas 211. For transmissions (e.g.,from transmitting feed elements 128 of a feed array assembly 127), therelative phases, and sometimes amplitudes, of the transmitted signalsare adjusted, so that the energy transmitted by feed elements 128 willconstructively superpose at a desired location (e.g., at a location of aspot beam coverage area 126). This phase and/or amplitude adjustment iscommonly referred to as applying beam weights (e.g., beamformingcoefficients) to the transmitted signals. For reception (e.g., byreceiving antenna feed elements 128 of a feed array assembly 127, etc.),the relative phases, and sometimes amplitudes, of the received signalsare adjusted (e.g., by applying the same or different beam weights) sothat the energy received from a desired location (e.g., at a location ofa spot beam coverage area 126, etc.) by antenna feed elements 128 willconstructively superpose for a given spot beam coverage area 126. Theterm beamforming may be used to refer to the application of the beamweights, whether for transmission, reception, or both. Adaptivebeamformers include the function of dynamically computing the beamweights. Computing the beam weights may require direct or indirectdiscovery of the communication channel characteristics. The processes ofbeam weight computation and beam weight application may be performed inthe same or different system components.

Spot beams 125 may be steered, selectively formed, and/or otherwisereconfigured by applying different beam weights. For example, a numberof active native feed element patterns, spot beam coverage areas 126,size of spot beams, relative gain of native feed element patterns and/orspot beams 125, and other parameters may be varied over time. Suchversatility is desirable in certain situations. Antenna assemblies 121that apply beamforming can generally form relatively narrow spot beams125, and may be able to form spot beams 125 having improved gaincharacteristics. Narrow spot beams 125 may allow the signals transmittedon one beam to be distinguished from signals transmitted on other spotbeams 125 to avoid interference, for example. Accordingly, narrow spotbeams 125 can allow frequency and polarization to be re-used to agreater extent than when larger spot beams 125 are formed. For example,spot beams 125 that are narrowly formed can service two discontiguousspot beam coverage areas 126 that are non-overlapping, while overlappingspot beams 125 can be made orthogonal in frequency, polarization, ortime. Greater reuse by use of smaller spot beams 125 can increase theamount of data transmitted and/or received. Additionally oralternatively, beamforming may be used to provide sharper gain rolloffat the beam edge may allow for higher beam gain through a larger portionof a spot beam 125. Thus, beamforming techniques may be able to providehigher frequency reuse and/or greater system capacity for a given amountof system bandwidth.

Some communications satellites 120 may use on-board beamforming (OBBF)to electronically steer signals transmitted and/or received via an arrayof feed elements 128. For example, a communications satellite 120 mayhave a phased array multi-feed per beam (MFPB) on-board beamformingcapability. The beam weights may be computed at a ground-basedcomputation center (e.g., at an access node terminal 130, at a networkdevice 141, at a communications service manager, etc.) and thentransmitted to the communications satellite 120 or may be pre-configuredat the communications satellite 120 for on-board application.

In some cases, significant processing capability may be needed at thecommunications satellite 120 to control the phase and gain of each feedelement 128 that is used to form spot beams 125. Such processing powermay increase the complexity of a communications satellite 120. Thus, insome cases, communications satellites 120 may operate with ground-basedbeamforming (GBBF) to reduce the complexity of the communicationssatellite 120 while still providing the advantage of electronicallyforming narrow spot beams 125.

FIGS. 4A and 4B illustrate an example of beamforming to form spot beamcoverage areas 126 from a native antenna pattern coverage area 221-cprovided by an antenna assembly 121 operating in a defocused condition,in accordance with aspects of the present disclosure. In FIG. 4A,diagram 400 illustrates native antenna pattern coverage area 221-c thatincludes multiple native feed element pattern coverage areas 211provided using a defocused multi-feed antenna assembly 121. Each of thenative feed element pattern coverage areas 211 may be associated with arespective feed element 128 of a feed array assembly 127 of the antennaassembly 121. In FIG. 4B, diagram 450 shows a pattern of spot beamcoverage areas 126 over a service coverage area 410 of the continentalUnited States. The spot beam coverage areas 126 may be provided byapplying beamforming coefficients to signals carried via the feedelements 128 associated with the multiple native feed element patterncoverage areas 211 of FIG. 4A.

Each of the spot beam coverage areas 126 may have an associated spotbeam 125 which may support a communications service within therespective spot beam coverage areas 126. Each of the spot beams 125 maybe formed from a composite of signals carried via multiple feed elements128 for those native feed element pattern coverage areas 211 thatinclude the respective spot beam coverage area 126. For example, a spotbeam 125 associated with spot beam coverage area 126-c shown in FIG. 4Bmay be a composite of signals from the eight feed elements 128associated with the native feed element pattern coverage areas 211-cshown with dark solid lines in FIG. 5A. In various examples, spot beams125 with overlapping spot beam coverage areas 126 may be orthogonal infrequency, polarization, and/or time, while non-overlapping spot beams125 may be non-orthogonal to each other (e.g., a tiled frequency reusepattern). In other examples, non-orthogonal spot beams 125 may havevarying degrees of overlap, with interference mitigation techniques suchas ACM, interference cancellation, or space-time coding used to manageinter-beam interference. Although generally discussed as downlink spotbeams 125 generated by applying appropriate beam weights to signalstransmitted from the feed elements 128, spot beams 125 for receivinguplink communications may also be processed by way of beamforming.

Beamforming may be applied to signals transmitted via the satelliteusing OBBF or GBBF receive/transmit signal paths. For a forward link ofthe service coverage area 410, one or more access node terminals 130 maytransmit respective forward uplink signals 132 to a communicationssatellite 120, which may then relay multiple forward downlink signals172 to multiple user terminals 150 within the service coverage area 410.Thus, the communications service provided to spot beam coverage areas126 illustrated in FIG. 4B may be based on the native antenna patterncoverage area 221-c of the antenna assembly as well as beam weightsapplied.

Although service coverage area 410 is illustrated as being provided viaa substantially uniform pattern of spot beam coverage areas 126 (e.g.,having equal or substantially equal beam coverage area sizes and amountsof overlap), in some examples spot beam coverage areas 126 for a servicecoverage area 410 may be non-uniform. For example, areas with higherpopulation density may be served by smaller spot beams 125 while areaswith lower population density may be served by larger spot beams 125. Insome cases, adjacent spot beams 125 may substantially overlap with eachother. For example, adjacent spot beams 125 may be configured to overlapat an area of high population density, therefore providing multipleoptions for serving a large number of users. Additionally oralternatively, multiple spot beams 125 of different sizes may beconfigured to serve an area, with only a subset of the spot beams 125being active at a given time. Thus, communications for particular userterminals 150 may be assigned to spot beams 125 that can carry thecommunications with greater efficiency (e.g., supporting bettermodulation and coding rate, etc.).

FIGS. 5A-5E illustrate an example of locations of spot beam coverageareas 126 of a service coverage area 410 a during differentcommunications service timeslots, in accordance with aspects of thepresent disclosure. In this example, the allocated spectrum is W Hz, andtwo polarizations (e.g., LHCP and RHCP) are available. At any instant oftime, 40 spot beams 125 having associated spot beam coverage areas 126may be active, 20 LHCP and 20 RHCP, although more or fewer spot beams125 may be active in actual implementations. Each spot beam 125 may usethe full W Hz of allocated spectrum, but only one polarization. In otherembodiments, each spot beam 125 may use only a portion of the allocatedspectrum. In the described example, a frame consists of Q=4 timeslots,although actual implementations may use frames with more or fewertimeslots. During each timeslot, the user receive and transmit spotbeams 125 may reside at different locations. The hopping pattern mayautomatically repeat at the conclusion of each frame or a new framedefinition may be applied to vary the hopping pattern.

FIG. 5A includes beam map 500 showing exemplary locations of spot beamcoverage areas 126 during the first timeslot of the frame. A spot beamcoverage area 126 labeled with an “L” in the center indicates a LHCPspot beam 125 and a spot beam coverage area 126 labeled with an “R”indicates a RHCP spot beam 125, although any number of otherpolarizations (e.g., linear polarizations) may be used in otherembodiments. Due to the small spot beam coverage area diameters, desiredlarge spread of the service coverage area 410-a, and the relativelysmall number of spot beams 125 active at one time, beams that use thesame polarization during a given timeslot may be spaced relatively farapart. This may lead to low interference levels between the spot beams125. The resulting high carrier to interference ratio (C/I) may help toincrease the capacity per spot beam 125. FIG. 5B includes beam map 510showing exemplary locations of spot beam coverage areas 126 during thesecond timeslot of the frame. FIG. 5C includes beam map 520 showingexemplary locations of spot beam coverage areas 126 during the thirdtimeslot of the frame. FIG. 5D includes beam map 530 showing exemplarylocations of spot beam coverage areas 126 during the fourth timeslot ofthe frame. As described in more detail below, each spot beam coveragearea 126 shown in FIGS. 5A-5D may be part of a dedicated receivepathway, a dedicated transmit pathway, or a hybrid transmit/receivepathway.

In each of the beam maps shown in FIGS. 5A-5D, spot beams 125 of thesame polarization are generally spaced very far apart (e.g., at themaximum distance possible). This spacing enables large values of C/I byminimizing interference from other active spot beams of the samepolarization. The selection of the actual locations for the spot beamcoverage areas 126 may depend on such factors as a desired servicecoverage area 410, the diameter of various spot beam coverage areas 126,the number of polarizations used, and the number of timeslots per frame.FIGS. 5A-5D provide just one example.

FIG. 5E includes beam map 540 showing a composite overlay of all thespot beam coverage areas 126 during all four timeslots (e.g., theservice coverage area 410-a). Only spot beams 125 of the same timeslotin FIG. 5E are active at the same time. Only spot beams 125 of the sametimeslot and the same polarization (e.g., LHCP or RHCP) present thepotential for significant interference. As mentioned above, the locationof these spot beam coverage areas 126 can be selected so as to maximizetheir spatial separation. Several geometric models may be used tomaximize the separation of spot beams 125 of like polarizations.

FIG. 6 shows an illustrative beam hopping frame 600, in accordance withaspects of the present disclosure. In the depicted example, Q=16timeslots per frame, and each timeslot occupies a 1.5 mSec intervalresulting in a total beam hopping frame duration of 24 mSec. A spot beam125, therefore, may be active in a given spot beam coverage area 126 fora minimum of 1.5 mSec or 1 timeslot, although a spot beam 125 may beactive in the same cell for more than 1 consecutive timeslot dependingon the timeslot definitions included in the beam hop frame definition.In some embodiments, a single region within the service coverage area410, denoted a cell, might only have one active spot beam 125 on theregion for one timeslot in the beam hopping frame. The length of thebeam hopping frame, therefore, may represent the potential waitingduration before information can be transmitted or received. It may bedesirable to use this architecture for low latency applications, such asvoice, so this hopping frame delay should be made insignificant relativeto other unavoidable delays. For example, for a satellite in aGeo-Synchronous Orbit (GSO), the one-way path delay (e.g., signalpropagation delay) is approximately 250 mSec and is an unavoidabledelay. Therefore, selection of a beam hopping frame length approximately1/10 this value or less renders the framing delay insignificant relativeto the unavoidable one-way path delay. Thus for a GSO satellite a framesize on the order of 25 mSec is generally adequate. Shorter frame sizesmay not significantly change the total delay experienced, as it isdominated by the one-way path delay, and will generally result in moreoverhead and increased complexity due to the fact that the spot beams125 are hopping faster. Thus, a beam hopping frame size of approximately25 mSec is suitable for most applications.

In other embodiments, more than one spot beam 125 may be active in acell during a single frame. For example, regions or cells may beassigned priorities indicative of the maximum acceptable delay forsupported applications with the region or cell. Assigned priorities maythen be used, at least in part, to determine the number of active spotbeams 125 in a particular region or cell per frame. For example, tosupport higher bandwidth or lower latency applications within a regionor cell, the region or cell may be assigned a higher priority than aregion or cell supporting lower bandwidth or higher latencyapplications. Cells or regions assigned higher priorities may have morethan one active spot beam 125 covering that cell or region in a singleframe. Any number of priorities may be defined corresponding to anynumber of active spot beams 125 for an individual cell per frame. Asingle cell may have a maximum of Q transmit spot beams 125 and Qreceive spot beams 125 active in that cell in a single frame (e.g.,beams are active in the cell during all timeslots). In some embodiments,a transmit spot beam 125 and a receive spot beam 125 may be active inthe same cell during the same timeslot, allowing for both transmissionand reception of data in the same timeslot.

FIG. 7 shows a block diagram for part of exemplary satellitearchitecture 700, in accordance with aspects of the present disclosure.The satellite architecture 700 includes a satellite 120 a with a firstantenna assembly 121-c and a second antenna assembly 121-d, each withrespective feed array assemblies 127 having a plurality of antenna feedelements 128. Antenna feed elements 128 are shown for both LHCP and RHCPto support multiple polarizations. In some embodiments (not shown), asatellite architecture may support only a single polarization. In otherembodiments, a satellite architecture may operate with a singlepolarization although it supports multiple polarizations.

Two separate antenna assemblies 121-c and 121-d are used in theexemplary satellite architecture 700, one for Rx (e.g., antenna assembly121-c) and one for Tx (e.g., antenna assembly 121-c), but an integratedTx/Rx antenna assembly 121 could also be used. Each antenna assemblyincludes a reflector 122, which is illuminated by a respective feedarray assembly 127 (e.g., a phased array) consisting of L feed elements128 in the feed array assembly 127. Satellite architecture 700 uses aphased array fed reflector as its antenna system, but Direct RadiatingArray (DRA) or any other type of phased array based antenna assembly 121that uses a beamforming network may be used in other embodiments. The Rxantenna assembly 121-c includes a feed array assembly 127-c havingL_(rx) feed elements 128-c in the phased array, and the output of eachfeed element port (e.g., feed element Rx signals) may be connected to aLow Noise Amplifier (LNA). Each LNA may be located near the associatedfeed element 128-c to minimize the system noise temperature. Ideally,the LNAs may be attached directly to the feed elements 128-c, which willyield an optimal noise figure. The output of each of the 2×L_(rx) LNAsis routed to Rx beamforming network (BFN) 710-a, which is composed ofboth LHCP and RHCP sections. Since the system noise figure isessentially set by the LNAs, Rx BFN 710 a can be located away from theLNAs with an interconnection of, for example, coaxial cable or awaveguide. Rx BFN 710 a may take the 2×L_(rx) inputs and provide Koutput signals, each corresponding to one of the K Rx spot beams 125. RxBFN 710 a may operate at the Rx frequency and provide no frequencytranslation, in this example.

The K outputs of Rx BFN 710 a from both the LHCP and RHCP sections maybe fed through K signal pathway hardware sections. In some embodiments,the same number of pathways are used for each available polarization(e.g., LHCP and RHCP), although in general there may be a differentnumber of pathways connected to the received signals of eachpolarization. Each pathway of the bent-pipe architecture typicallyconsists of a frequency conversion process, filtering, and selectablegain amplification. Other forms of processing (e.g., demodulation,remodulation, or remaking of the received signals, like in a“regenerative” system) are not performed when using a bent-pipearchitecture. In a bent-pipe architecture, the frequency conversion maybe required to convert the spot beam signal at the uplink frequency to aseparate downlink frequency, for example. The filtering generallyconsists of pre-filtering before the downconverter and post-filteringafter the downconverter and is present to set the bandwidth of thesignal to be transmitted as well as to eliminate undesired mixerintermodulation products. The selectable gain channel amplifier mayprovide independent gain settings for each of the K pathways in theexample of FIG. 7.

Tx BFN 710-b, which may include both LHCP and RHCP sections, maygenerate 2×L_(tx) outputs from the K pathway output signals. In someembodiments, the pathway output signals that derive from an LHCP receivespot beam 125 may be output on a RHCP transmit spot beam 125, and viceversa. In other embodiments, the pathway output signals that derive froman LHCP receive spot beam 125 may be output on a LHCP transmit spot beam125. Tx BFN 710-b may operate at the Tx frequency and may provide nofrequency translation in this example. The outputs of Tx BFN 710-b arerouted to 2×L_(tx) high power amplifiers (HPAs). The harmonic filters(HF) connected to the output of each HPA may perform low pass filteringto provide suppression of the 2^(nd) and higher order harmonics, forexample, from the output of the HPAs. The output of the harmonic filters(e.g., feed element Tx signals) may then be input to the 2×L_(tx) feedelements 128-d in the Tx feed array assembly 127-d. Each HPA andharmonic filter may be located close to the associated Tx feed element128-d to minimize the losses. Ideally, the HPA/HFs may be attacheddirectly to the Tx feed elements 128-d, which may yield an optimalradiated power.

As shown in FIG. 7, separate reflectors (e.g., reflectors 122-c and122-d), and separate feed array assemblies (e.g., feed array assemblies127-c and 127-d) may be used for the Tx and Rx spot beams 125. However,as described above, in some embodiments a single reflector 122 and asingle feed array assembly 127 may be used to perform both Tx and Rxfunctions. In these embodiments, each feed element 128 may include twoports, one for Tx and one for Rx. For a system using two polarizations(e.g., RHCP and LHCP), a 4-port feed element (2 for Tx and 2for Rx) maybe included. To maintain acceptable Tx to Rx isolation, such a singlereflector 122 approach may also employ diplexers or other filteringelements within some or all of the feed elements 128. These filteringelements may pass the Rx band while providing suppression in the Txband. The increased number of feed elements 128 and the phase matchingrequirements for the BFNs 710 can make this approach more complex toimplement but may reduce costs associated with multiple reflectors 122and multiple feed array assemblies 127.

In some embodiments, Rx BFN 710 a, Tx BFN 710-b, or both, may usetime-varying beam weight sets to hop receive spot beam coverage arealocations, transmit spot beam coverage area locations, or both, aroundover time. These beam weight sets may be stored in Beam Weight Processor(BWP) 714. BWP 714 may also provide the control logic to generate theproper beam weights at the proper times. BWP 714 may be connected to theground via bi-directional data link 716, which can be in-band with thetraffic data or out-of-band with its own antenna assembly 121 andtransceiver. Bi-directional data link 716 is shown as bi-directional inthe example of FIG. 7 to assure that the correct beamforming weight setshave been received by BWP 714. As such, error detection and/orcorrection techniques, including retransmission requests, may besupported using the bi-directional link. In other embodiments, auni-directional link is used with error detection and/or correction. Insome embodiments, an initial beamforming weight set can be loaded intothe memory of BWP 714 before launch.

Data link 716 may be used, for example, to receive pre-computed beamweights and deliver such weights to BWP 714. In some embodiments, thebeam weights are generated on the ground at a network device 199 such asa network management entity or a Network Operational Center (NOC). Thedesired locations of each of the K Tx and Rx beams, along with thenative feed element patterns 210, may be used to generate the beamweight values. There are several techniques for generating appropriatebeam weights given the desired spot beam coverage area locations. Forexample, in one approach, beam weights may be generated on the ground innon-real time. The dynamic weights may then be uploaded to BWP 714through data link 716, and then applied to the BFNs in a dynamic mannerto produce hopping beams on both the Rx uplink and the Tx downlink.

The downlink portion of data link 716 may be used to report the statusof the BFNs 710 and to provide confirmation of correct reception of theuplinked beam weights. Correct reception of the beam weight sets can bedetermined by use of a traditional CRC code, for example. In the eventof incorrect reception, as indicated by a failure of the CRC to check,for example, the uplink transmission of the beam weight sets (or theportion of the beam weight sets that was deemed incorrect or invalid),may be retransmitted. In some embodiments, this process may becontrolled by an automatic repeat request ARQ retransmission protocol(such as, for example, selective repeat ARQ, stop-and-wait ARQ, orgo-back-N ARQ, or any other suitable retransmission, error detection, orerror correction protocol) between the ground station and BWP 714.

In general, satellite architecture 700 provides for K generic hoppingpathways. Each pathway functionally consists of an Rx spot beam 125 anda Tx spot beam 125, connected together through electronics and circuitrythat provide signal conditioning, such as one or more of filtering,frequency conversion, amplification, and the like. The pathways may eachbe represented as bent pipe transponders that can be used in a hub-spokeconfiguration or a mesh configuration. For example, in one embodimentwith a mesh configuration, a pathway carries signals between a firstplurality of terminals and a second plurality of terminals via thesatellite. In accordance with the systems and methods described herein,the termination points (e.g., the Tx spot beam coverage area locationand Rx spot beam coverage area location) for each pathway may be dynamicand programmable, resulting in a highly flexible satellitecommunications architecture.

FIG. 8 shows block diagram 800 of one polarization of an exemplary RxBFN 710-c, in accordance with aspects of the present disclosure. Thereceive BFN 710-c may take in feed element Rx signals from L_(rx) feedelements 128 and provides the spot beam signals of K_(p) LHCP and RHCPformed spot beams 125 as outputs. In this example, there are K_(p)=K/2LHCP receive spot beams 125 and K/2 RHCP receive spot beams 125 althoughdifferent numbers of receive spot beams 125 of each polarization may beused in other embodiments.

Each feed element Rx signal from a feed element 128 is first split, viasplitters 802, into K identical copies, one for each spot beam 125. ThenK_(p) parallel beamformers are realized. Each beamformer may include,among other components, amplitude and phase adjustment circuitry 804 andsummer 806. Each instance of amplitude and phase adjustment circuitry804 may take an input signal from one of the L_(rx) splitters andprovide an amplitude and phase adjustment to the signal (e.g., viareceive beam weights of a receive beamforming weight vector associatedwith an Rx spot beam 125). The L_(rx) amplitude and phase adjustedsignals may then be summed using summer 806 to produce the spot beamsignal from one formed spot beam 125. Each Rx spot beam signal may thenbe fed into one of K_(p) independent signal pathways as discussedherein. The beamforming vector coefficients used to create the Rx spotbeam signal of pathway 1 of the antenna assembly 121 are shown by dashedline 808 in FIG. 8.

The process of adjusting the amplitude and phase of the signals may bemathematically described as the multiplication of the complex base bandrepresentation of the signal by a complex number (e.g., a complexweight). Letting the complex number be represented as w=I+jQ, themagnitude of w is the amplitude adjustment and the phase of w is thephase adjustment. In practice the amplitude and phase adjustment can berealized in a number of ways. Two common techniques in phased arrayantenna assemblies 121 are vector multiplier circuits that take as aninput the I and Q values, and circuits that have independent phase andamplitude adjustment mechanisms and take as input the desired amplitudeand phase adjustments. One should recognize I+jQ as the rectangularcoordinates of the complex number, w, and Amplitude/Phase as the polarcoordinates of the complex number, w. Rx BFN 710-c may provide dynamic(changing) and programmable complex beam weight values on each of the Kbeamformers in both halves of the Rx BFN 710-c. In practice, a Rx BFN710-c may generally have amplification stages within the Rx BFNstructure to account for some or all of the insertion losses of thedevices used to perform the Rx BFN functions (e.g., splitting,weighting, and combining).

The signal processing of the Rx BFN 710-c may be carried out in theanalog and/or digital signal domain. For example, when signal processingis carried out by the Rx BFN 710-c in the digital domain, the Rx BFN710-c may include one or more analog-to-digital converters (e.g.,converting the L_(rx) feed element Rx signals to the digital domain). Inother examples, each of the feed elements 128 may be associated with itsown analog-to-digital converters that provides a digital signal to theRx BFN 710-c. In various examples that include digital domainprocessing, the pathway hardware may provide spot beam signals in thedigital domain, or may include one of more digital-to-analog convertersto convert the spot beam signals of the pathway hardware into the analogdomain. In other examples, the signal processing of the Rx BFN 710-c maybe carried out entirely in the analog domain, such that the L_(rx) feedelement signals are received in the analog domain, and processed signalsremain in the analog domain through the pathway hardware that providesthe spot beam signals in the analog domain.

FIG. 9 shows block diagram 900 of one polarization of an exemplary TxBFN 710-d, which may be referred to as a feed forming network (FFN), inaccordance with aspects of the present disclosure. The Tx BFN 710-dtakes in signals from K_(p) signal pathways (e.g., K/2 LHCP and K/2 RHCPpathways) and provides feed element Tx signals to each of the L_(tx)feed elements 128. Each input signal from a pathway is first split, viasplitters 902, into L_(tx) identical copies, one for each feed element128. Then L_(tx) parallel “feed formers” are realized. Each feed formermay include amplitude and phase adjustment circuitry 904 and summer 906.Amplitude and phase adjustment circuitry 904 may take an input spot beamsignal from one of the K_(p) splitters, and provide an amplitude andphase adjustment (e.g., via transmit beam weights of a transmit beamweight vector associated with a Tx spot beam 125). The L_(tx) amplitudeand phase adjusted feed element Tx component signals are then summedusing summer 906 to produce the feed element Tx signal for transmissionby one feed element 128.

The process of adjusting the amplitude and phase of the signal may bemathematically described as multiplication of the complex base bandrepresentation of the signal by a complex number (e.g., a complexweight). Letting the complex number be represented as w=I+jQ, themagnitude of w is the amplitude adjustment and the phase of w is thephase adjustment. In practice, the amplitude and phase adjustment can berealized a number of ways (e.g., as described above with regard to FIG.8). The first and last beamforming vector coefficients used to form theTx spot beam 125 of pathway 1 of the satellite are shown by dashed line908. The remaining coefficients are not explicitly shown in the exampleof FIG. 9.

The signal processing of the Tx BFN 710-d may be carried out in theanalog and/or digital signal domain. For example, when signal processingis carried out by the Tx BFN 710-d in a digital domain, the Tx BFN 710-dmay include one or more analog-to-digital converters (e.g., convertingthe K spot beam signals to the digital domain). In other examples, eachof the K spot beam signals may be provided by the pathway hardware tothe Tx BFN 710-d as a digital signal. In various examples that includedigital domain processing, the Tx BFN 710-d may provide the L_(tx) feedelement Tx signals in the digital domain (e.g., to be converted to ananalog signal at a respective feed element 128 by an associateddigital-to-analog converter), or may include one or moredigital-to-analog converters to convert the feed element Tx signals intothe analog domain. In other examples, the signal processing of the TxBFN 710-d may be carried out entirely in the analog domain, such thatthe K spot beam signals are received in the analog domain, and processedsignals remain in the analog domain through the beamforming hardwarethat provides the L_(tx), feed element signals in the analog domain.

As described above with regard to the Rx BFN 710-c, the Tx BFN 710-d mayprovide dynamic (changing) and programmable complex beam weight valueson each of the K feed formers in the Tx BFN 710-d. In practice, the TxBFN 710-d will also have amplification stages within the Tx BFNstructure to make up for some or all of the insertion losses of thedevices used to perform the Tx BFN functions (e.g., splitting,weighting, and combining).

FIG. 10 shows a block diagram of an illustrative system 1000 for GBBFfor forward link signal transmission, in accordance with aspects of thepresent disclosure. The components of the system 1000 may be distributedbetween a ground segment 102-a (e.g., including access node terminal(s)130, network device(s) 141, etc.) and a space segment 101-a (e.g.,including communications satellite(s) 120-b), and illustrate an exampleof implementing a transmit beamforming network at a ground segment.

The ground segment 102-a of the system 1000 may receive, as an input,communications service traffic 1005 that is destined for one or moreuser terminals 150. The communications service traffic 1005 may bereceived from one or more networks 140, from one or more network devices141, and/or one or more access node terminals 130. The communicationsservice traffic 1005 may be provided to one or more traffic managers1020, which may allocate portions of the communications service traffic1005 to one or more spot beams 125. The traffic manager 1020 may havelocation information for the target devices and may assign portions ofthe communications service traffic 1005 to spot beams 125 based on thelocations of the intended target device (e.g., the target userterminal(s) 150) relative to the spot beam coverage areas 126 (e.g.,assigning communications service traffic 1005 for a given target deviceto a spot beam 125 for which the given target device is located withinthe corresponding spot beam coverage area 126). In various examples, theground segment 102-a of the system 1000 may have a traffic manager 1020for all communications service traffic 1005 (e.g., in a networkmanagement entity or other network device 141), or the ground segment102-a of the system 1000 may have a distributed plurality of trafficmanagers 1020 (e.g., co-located with a plurality of access nodeterminals 130).

The traffic manager 1020 generates K Tx spot beam signals 1025containing the portions of the communications service traffic 1005destined for the various target devices, where K may be the number ofspot beams 125 simultaneously supported by the system 1000. The Tx spotbeam signals 1025 may be provided by separate digital or analog hardwarepathways (e.g., the K signal pathway hardware section as described withreference to FIG. 7), or may be logical channels embodied in software.The Tx spot beam signals 1025 may be provided to a Tx BFN 710-e, whichmay be co-located with the traffic manager 1020 (e.g., at a networkdevice 141 or an access node terminal 130 including the traffic manager1020), or may be located at another device of the ground segment 102-a(e.g., a transmitting access node terminal 130 that does not include thetraffic manager 1020).

The Tx BFN 710-e may be an example of Tx BFNs 710 as described herein,and be coupled between the K spot beam signal pathways and atransmitting device such as an access node terminal 130. The Tx BFN710-e generates L_(tx) feed element component signals 1028, where L_(tx)may be the number of antenna feed elements 128 used by thecommunications satellite 120-b to support forward link transmissions ofthe communications service. Tx BFN 710-e may receive a beamformingweight set 1027 from a BWP 714-a, and apply beam weights to the receivedTx spot beam signals 1025 to generate the feed element component signals1028 that will be used to form the respective spot beams 125. BWP 714-amay provide beamforming weight set 1027 according to any of thetechniques described herein, including applying beam weights accordingto time slots of a beam hopping configuration, adjustments according toa native antenna pattern, adjustments according to an orbital positionof the communications satellite 120-b, and combinations thereof.

The process of applying beam weights to generate the respective feedelement component signals 1028 may be similar to the process forgenerating feed element Tx signals described with reference to FIG. 9.However, because the feed element component signals 1028 are notdirectly transmitted by feed elements of the ground segment 102-a, thefeed element component signals 1028 are not required to have the samecharacteristics (e.g., frequency, polarization, time synchronization,etc.) as those that are transmitted by a communications satellite 120-bof the space segment 101-a. Rather, the feed element component signals1028 need only to be formatted in a manner that may be later used togenerate feed element Tx signals transmitted by the communicationssatellite 120-b of the space segment 101-a (e.g., feed element Txsignals 1085).

The feed element component signals 1028 may be provided to a multiplexer1030, which may combine the feed element component signals 1028 togenerate a multiplexed uplink signal 1035. The multiplexer 1030 may beco-located with the Tx BFN 710-e (e.g., at a network device 141 or anaccess node terminal 130), or may be located at another transmittingdevice of the ground segment 102-a (e.g., a transmitting access nodeterminal 130). The feed element component signals 1028 may be combinedby frequency-division multiplexing, time-division multiplexing,code-division multiplexing, or any other form of multiplexing thatsupports communication of the information of feed element componentsignals 1028 in a separable manner. The multiplexed uplink signal 1035may be provided to a transmitter 1040 of the ground segment 102-a, whichmay be an example of an access node terminal antenna system 131described with reference to FIG. 1. The transmitter 1040 transmits themultiplexed uplink signal 1035 in a feeder uplink signal 1045 (e.g., viaan access node terminal antenna 131, etc.) to the communicationssatellite 120-b.

The communications satellite 120-b receives, via an antenna (e.g., anantenna assembly 121 or another type of antenna), the feeder uplinksignal 1045 at a receiver 1060. Receiver 1060 may perform variousoperations including demodulation, down-conversion (e.g., to anintermediate frequency or a baseband frequency, etc.) to generatereceived multiplexed uplink signal 1065. The received multiplexed uplinksignal 1065 may be provided to a demultiplexer 1070, which separates thereceived multiplexed uplink signal 1065 into L_(tx) feed element Txcomponent signals 1075, where L_(tx) is the number of feed elements128-e of a feed array assembly 127-e used by an antenna assembly 121-efor transmitting forward link signals. The demultiplexer 1070 maysupport frequency-division demultiplexing, time-division demultiplexing,code-division demultiplexing, or any other demultiplexing that canseparate the feed element Tx component signals 1075 from the receivedmultiplexed uplink signal 1065.

In some examples, a communications satellite 120-b may have more thanone receiver 1060, which may each be associated with a different feederuplink signal 1045, and each receiver 1060 may be associated with aseparate demultiplexer 1070. In some examples, different feeder uplinksignals 1045 may be transmitted by separate access node terminals 130 ofthe ground segment 102-a, and different feeder uplink signals 1045 maybe associated with different sets of spot beams 125. For example, eachfeeder uplink signal 1045 may include Tx component signals 1075 for asubset of spot beams supported by the GBBF architecture. In one example,each feeder uplink signal 1045 is associated with a particular “color”as described herein (e.g., feeder uplink signals 1045 and 1045-a beingdifferent colors from each other, or otherwise orthogonal to eachother). In other examples, each feeder uplink signal 1045 is associatedwith Tx component signals 1075 corresponding to different sets of spotbeams (e.g., which may be orthogonal or non-orthogonal in frequency andpolarization). For example, the communications satellite 120-b mayinclude a second receiver 1060 a, and a second demultiplexer 1070 a,which may provide a second set of feed element Tx component signals1075-a. In various examples, the receiver 1060 and additional receivers1060 (e.g., receiver 1060-a) may be associated with separate antennas(e.g., separate antenna assemblies 121), or may be associated withseparate portions of the same antenna.

In some examples, the set of feed element Tx component signals 1075 maybe combined with the second set of feed element Tx component signals1075-a, for each respective feed element 128, by a plurality of summers1080 (e.g., summers 1080-a-1 through 1080-a-L_(tx), associated with feedelements 128-e-1 through 128-e-L_(tx), as shown). The summers 1080 mayprovide a set of feed element Tx signals 1085 to the feed array assembly127-e for transmission. In examples with a single receiver 1060,receiving a single feeder uplink signal 1045 from a single access nodeterminal 130, the feed element Tx component signals 1075 may besubstantially equivalent to the feed element Tx signals 1085 describedherein. In some examples the feed element Tx signals 1085 may be anoutput of a signal processor (e.g., an analog signal processor or adigital signal processor) of the communications satellite 121-e thatincludes demultiplexer(s) 1070, the summer(s) 1080, and/or any othercomponents for providing the feed element Tx signals 1085, which may bea dedicated transmission signal processor, or may share components witha reception signal processor (e.g., the signal processor described withreference to illustrative system 1100 of FIG. 11). In other examples,each feeder uplink signal 1045 is associated with Tx component signals1075 for a different set of Tx elements 128-e. In this example, GBBFsystem 1000 does not include summers 1080 and Tx component signals 1075are coupled with a first subset of feed elements 128-e while Txcomponent signals 1075-a are coupled with a second subset of feedelements 128-e.

The feed element Tx signals 1085 may be provided to the feed elements128 (e.g., feed elements 128-e-1 through 128-e-L_(tx)) of the feed arrayassembly 127-e, which may convert the electrical feed element Tx signals1085 to electromagnetic wave energy of feed element signal transmissions1095, thus providing the communications service traffic 1005 to reachthe various target devices. As a result of the beamforming applied tothe Tx spot beam signals 1025 by the Tx BFN 710-e, the feed elementsignal transmissions 1095 may form spot beams 125, and reach the targetdevices located in the associated spot beam coverage areas 126. Thus,the communications satellite 120-b may transmit the communicationsservice traffic 1005 via feed elements 128-e, according to spot beams125 assigned by the ground segment 102-a, and a beamforming weight set1027 applied at the ground segment 102-a. By performing such beamformingat the ground segment 102-a, the communications satellite 120-e may beless complex than a communications satellite 120 that performsbeamforming at the communications satellite 120 (e.g., communicationssatellite 120 a described with reference to FIG. 7). This reducedcomplexity provided by GBBF may, for example, reduce satellitedeployment weight, satellite cost, satellite power consumption, and/orsatellite failure modes, while providing comparable service as acommunications satellite that performs OBBF.

FIG. 11 shows a block diagram of an illustrative system 1100 for GBBFfor return link signal transmission, in accordance with aspects of thepresent disclosure. The components of the system 1100 may be distributedbetween a ground segment 102-b (e.g., including access node terminal(s)130, network device(s) 141, etc.) and a space segment 101-b (e.g.,including communications satellite(s) 120-c), and illustrate an exampleof implementing a receive beamforming network at a ground segment. Insome examples, the ground segment 102-b may share components with aground segment 102-a as described with reference to FIG. 10 (e.g.,supporting GBBF for forward link and return link at a common access nodeterminal 130, sharing a common traffic manager 1020 or 1120, etc.).Similarly, in some examples the space segment 101-b may share componentswith a space segment 101-a as described with reference to FIG. 10 (e.g.,supporting forward link and return link communications on the samecommunications satellite 120). In other examples, separatecommunications satellites may be used for forward link and return linkcommunications (e.g., communications satellite 120-b for forward linkcommunications, and a different communications satellite 120-c forreturn link communications).

The space segment 101-b of the system 1100 may receive (e.g., at anantenna assembly 121-f of communications satellite 120-c) return linkcommunications signals 1195 of a communications service, and associatedwith communications service traffic 1105, where the return linkcommunications signals 1195 may have been transmitted by one or moresource devices (e.g., user terminals 150). The return linkcommunications signals 1195 may be received at a plurality of antennafeed elements 128-f (e.g., feed elements 128-f-1 through 128-f-L_(rx))of the feed array assembly 127-f, and converted from electromagneticwave energy to L_(rx) electrical feed element Rx signals 1185, whereL_(rx) is the number of feed elements 128-f used for receiving returnlink communications. In some examples the feed array assembly 127-f usedfor return link communications may share components with a feed arrayassembly 127 used for forward link communications (e.g., usingtransceivers at common feed elements 128 as a feed array assembly 127-edescribed with reference to FIG. 10). In other examples, feed arrayassembly 127-f used for return link communications may be an entirelydifferent assembly than a feed array assembly 127 used for forward linkcommunications (e.g., a feed array assembly 127-f for reception beingseparate from a feed array assembly 127-e for transmission as describedwith reference to FIG. 10).

Although various components of the return link communications signals1195 may have been transmitted by a plurality of source devices fromvarious locations of a return link service coverage area 410, thecomponents of the return link communications signals 1195 are not yetassociated with particular spot beams 125. Rather, the return linkcommunications signals 1195 may be received by respective feed elements128-f-1 through 128-f-L_(rx) in a manner where signals of a particularfrequency and/or polarization may have characteristic phase and/oramplitude offsets that may be used to determine a direction from whichparticular components of the return link transmissions 1095 weretransmitted from, thereby associating particular components of thereturn link transmissions 1095 with a particular spot beam 125 andproviding a spatial degree of orthogonality for signal reception.Because the reception beamforming calculations are not performed on thecommunications satellite 120-c, the feed element Rx signals 1185 aremaintained in separate form (e.g., by separate wiring), and provided tomultiplexer 1170.

In some examples the multiplexer 1170 may combine the feed element Rxsignals 1185 to generate a multiplexed downlink signal 1165, which isprovided to transmitter 1160. The feed element Rx signals 1185 may becombined by frequency-division multiplexing, time-division multiplexing,code-division multiplexing, or any other form of multiplexing thatsupports the communication of information of feed element Rx signals1185 in a separable manner. In some examples, the multiplexer 1170 usedfor return link communications may share components with a demultiplexer1070 used for forward link communications as described with reference toFIG. 10, and in other examples a multiplexer 1170 and a demultiplexer1070 may be entirely separate components of a communications satellite120 (e.g., separate signal processing chains.). In some examples themultiplexed downlink signal(s) 1165 may be an output of a signalprocessor (e.g., an analog signal processor or a digital signalprocessor) of the communications satellite 121-f that includes thesplitter(s) 1180, the multiplexer(s) 1070, and/or other components forproviding the multiplexed downlink signal(s) 1165, which may be adedicated reception signal processor, or may share components with atransmission signal processor (e.g., the signal processor described withreference to illustrative system 1000 of FIG. 10).

The communications satellite 120-c transmits the multiplexed downlinksignal 1165 in a feeder downlink signal 1145 to the ground segment 102-bvia transmitter 1160 (e.g., by an antenna assembly 121 or another typeof antenna). In some examples the transmitter 1160 used for return linkcommunications may share components with a receiver 1060 used forforward link communications (e.g., using a transceiver of a commonantenna). In other examples, transmitter 1160 used for return linkcommunications may be an entirely different assembly than a receiver1060 used for forward link communications (e.g., using separate antennaassemblies 121, using a separate transmitter and receiver that share acommon reflector, etc.).

In some examples the communications satellite 120-c may includesplitters 1180-a that split the feed element Rx signals 1185 into feedelement Rx component signals 1175 to feed a plurality of multiplexers1170 (e.g., first multiplexer 1170 and second multiplexer 1170-a). Thesplitters 1180 a may split the feed element Rx signals 1185 intodifferent frequency or polarization components, for example, which maybe associated with different colors as described herein. In someexamples the second multiplexer 1170 a may generate a second multiplexeddownlink signal 1165-a, which may be provided to a second transmitter1160 a (though in some examples the transmitters 1160 and 1160 a may bethe same transmitter, or otherwise share components of a commontransmitter 1160). The second transmitter 1160 a may transmit the secondmultiplexed downlink signal 1165-a in a second feeder downlink signal1145-a, which may be a feeder downlink signal associated with adifferent color than the feeder downlink signal 1145. In some examplesdifferent access node terminals 130 may be associated withcommunications of different colors, and thus the feeder downlink signals1145 and 1145-a may be provided to different access node terminals 130.In other examples, different multiplexers 1170 may be coupled withdifferent subsets of feed elements 128-f, such that different feederdownlink signals 1145 are associated with spot beams 125 supported bydifferent subsets of feed elements 128-f.

The ground segment 102-b may receive, as an input, the feeder downlinksignal 1145 at a receiver 1140, which may be an example of an accessnode terminal antenna system 131. In some examples the receiver 1140used for return link communications may share components with atransmitter 1040 used for forward link communications (e.g., using atransceiver of a common access node terminal 130). In other examples, areceiver 1140 used for return link communications may be an entirelydifferent assembly than a transmitter 1040 used for forward linkcommunications (e.g., using separate access node terminal antennasystems 131 at the same access node terminal 130, using a separatetransmitter and receiver that share a common reflector of an access nodeterminal antenna system 131, using an entirely separate access nodeterminal 130, etc.).

The received multiplexed downlink signal 1135 may be provided to ademultiplexer 1130, which separates the received multiplexed downlinksignal 1165 into L_(rx) feed element component signals 1128. Thedemultiplexer 1070 may support frequency-division demultiplexing,time-division demultiplexing, code-division demultiplexing, or any otherdemultiplexing that can separate the feed element component signals 1128from the received multiplexed downlink signal 1135. In some examples,the demultiplexer 1130 used for return link communications may sharecomponents with a multiplexer 1030 used for forward link communicationsas described with reference to FIG. 10, and in other examples ademultiplexer 1130 and a multiplexer 1030 may be entirely separatecomponents of a communications satellite 120 (e.g., separate signalprocessing chains.). The demultiplexer 1130 may subsequently provide thefeed element component signals 1128 to an Rx BFN 710-f.

The Rx BFN 710-f may be an example of Rx BFNs 710 as described herein,and may be coupled between the receiver 1140 and the K spot beam signalpathways. The Rx BFN 710-f generates K Rx spot beam signals 1125containing portions of communications service traffic 1105 as receivedfrom the various source devices, where K may be the number of spot beams125 simultaneously supported by the system 1100 for return linktransmissions of the communications service. Rx BFN 710-f may receive abeamforming weight set 1127 from a BWP 714-b, and apply beam weights tothe feed element component signals 1128 to generate the Rx spot beamsignals 1125. BWP 714-b may provide beamforming weight set 1127according to any of the techniques described herein, including applyingbeam weights according to time slots of a beam hopping configuration,adjustments according to a native antenna pattern, adjustments accordingto an orbital position of the communications satellite 120-c, andcombinations thereof.

The process of applying beam weights to generate the respective Rx spotbeam signals 1125 may be similar to the process for generating Rx spotbeam signals described with reference to FIG. 8. However, because thefeed element component signals 1028 are not directly received by feedelements of the ground segment 102-b, the feed element component signals1128 are not required to have the same characteristics (e.g., frequency,polarization, time synchronization, etc.) as those that are received bythe communications satellite 120-c of the space segment 101-b. Rather,the feed element component signals 1028 may have been converted in amanner to facilitate multiplexing/demultiplexing, feeder linktransmission, and/or the conversion by Rx BFN 710-f.

The Rx spot beam signals 1125 may subsequently be provided by the Rx BFN710-f to a traffic manager 1120. The Rx spot beam signals 1125 may beprovided by separate digital or analog hardware pathways (e.g., the Ksignal pathway hardware section as described with reference to FIG. 7),or may be logical channels embodied in software. As a result of the Rxbeamforming applied to the feed element component signals 1128, theinformation carried by components of the return link communicationssignals 1195 may be identified according to separate spot beams 125,thus separating communications signals according to an associated spotbeam coverage area 126 and supporting frequency reception reuse across areturn link service coverage area 410. The traffic manager 1120 maysubsequently provide the communications service traffic 1105 to, forexample, one or more other devices and/or networks, such as networks 140and/or network devices 141 described with reference to FIG. 1

Thus, the traffic manager 1120 may interpret return link signals of acommunications service according to a Rx spot beams 125 formed by abeamforming weight set 1127 applied at the ground segment 102-b. Byperforming such reception beamforming at the ground segment 102-b, thecommunications satellite 120-c may be less complex than a communicationssatellite 120 that performs beamforming at the communications satellite120 (e.g., communications satellite 120 a described with reference toFIG. 7). This reduced complexity provided by GBBF may, for example,reduce satellite deployment weight, satellite cost, satellite powerconsumption, and/or satellite failure modes, while providing comparableservice as a communications satellite that performs OBBF.

FIG. 12 shows block diagram of a system 1200 that employs an exemplarybeam weight processor (BWP) 714-c. Single or multiple board computer1202 (or equivalent) may be used to interface with a bi-directional datalink (e.g., data link 716 described with reference to FIG. 7) to acontrol station, which is typically a ground control station such as aNOC (e.g., a network device 141 as described with reference to FIG. 1).Generally, the NOC is different than the Telemetry, Tracking, andControl (TT&C) station, but it may be implemented in the TT&C ifdesired. The beam weights may be received for all the spot beams 125 andall timeslots. Computer 1202, which may include one or more processorscoupled to memory, may implement an ARQ protocol providing feedback datato the data link transmitter for transmission down to the controlstation. The feedback data may include a notification of successful orunsuccessful reception of the uplink data. Uplink data may include, forexample, beam weights, dwell times, pathway gains, commands, and anyother suitable data.

The BWP 714-c or affiliated hardware may provide the bulk storage for aplurality of beamforming weight matrices (e.g., a transmit beamformingweight set, a receive beamforming weight set, or a combination thereof).A beamforming weight matrix may include the set of all beamformingweight vectors used for transmission and reception of all spot beams 125in one timeslot. A beam weight vector may include the group of L_(tx) orL_(rx) individual complex beam weights used to create one spot beam 125during one timeslot. Thus, a transmit beamforming weight vector includesindividual complex transmit beam weights, while a receive beamformingweight vector includes individual complex receive beam weights.Beamforming weight matrices are generally computed at the controlstation based on the desired locations of spot beam coverage areas 126(e.g., the desired directions of the transmit spot beams 125, thereceive spot beams 125, or both) for each timeslot in the beam hopframe. A beam hop frame may include a sequence of beam hop timeslots,each timeslot with an associated dwell time. The dwell time may be fixedfor all slots, or the dwell time can be variable on a timeslot bytimeslot basis, with the dwell times potentially changing frame byframe. In one example, a dwell time can be the duration of a variablenumber of timeslots, where each timeslot is of fixed duration. Inanother example, a dwell time can be the duration of one or moretimeslots, where the durations of the timeslots vary.

In some embodiments, a beamforming weight set includes the set of allbeamforming weight vectors used for transmission and reception of allspot beams 125 in all timeslots of a beam hopping frame. Additionally oralternatively, a beam hop frame definition may include a linked list ofbeam hop timeslots. In the linked list approach, a dynamic dwell timefor each timeslot may be easily incorporated into the linked list. Anyother suitable data structure may also be used for frame definitions.The beam hop frame definition can also include pathway gains for settinga selectable gain channel amplifier for each pathway, for example, asillustrated in FIG. 7.

In an example communications satellite 120 using the beamforming weightset approach, a small number (e.g., tens) of beamforming weight sets canbe pre-computed and uploaded to a BWP 714 in a communications satellite120. These beamforming weight sets can then be switched into operationat any time via a single command from the ground indicating whichbeamforming weight set to use and at what time. This allows switchingbeamforming weight sets without requiring a significant amount ofinformation to be uploaded to the BWP 714. For example, in someembodiments, 24 complete beamforming weight sets are pre-computed,uploaded, and stored at the BWP 714-c (e.g., in memory 1204). Once anhour (or on any other suitable schedule), a different beamforming weightset may be selected for use by the BWP via the data link. This allowsthe spot beam coverage areas 126 and capacity allocation to track, forexample, the hourly variations of the demand on a daily or 24-hourbasis.

A beamforming weight set may include a significant amount of data. Forexample, in some embodiments, a beamforming weight set may include datacorresponding to L_(tx)+L_(rx) feed elements 128 (e.g., 1024), times Kpathways (e.g., 80), times Q timeslots (e.g., 64), times the number ofbits required per beam weight (e.g., 12, 6 bits for I and 6 bits for Q).For example, in FIG. 12, this sums to approximately 16 MB of data perweight set. Data and command uplink to the satellite may typically notbe very fast. Even at a 1 Mbps data link, it would take 128 seconds toupload the 16 MB beamforming weight set. Thus, pre-loading manybeamforming weight sets in non-real time may be more convenient forcertain applications where a BWP 714 is located at a satellite. When aBWP 714 is part of a ground segment 102 (e.g., ground segment 102-adescribed with reference to FIG. 10), such considerations may not becritical.

One of the stored beamforming weight sets in the BWP 714-c may beselected as the active beamforming weight set and used in the generationof the hopped spot beams 125. This active beamforming weight set may bestored in memory 1204, such as a dual port RAM, that allows computer1202 to load the next active beamforming weight set and some externallogic to dynamically access the individual beamforming weight vectors ofthe current active beamforming weight set. The individual beamformingweight vectors of the active beamforming weight set may then be outputas beamforming weights at the proper time under control of sequentiallogic 1206. An example of sequential logic 1206 may include timeslotcounter 1208 that is incremented once per timeslot. Timeslot counter1208 may be a simple 6-bit counter in some embodiments and may handleframes with up to 2⁶=64 timeslots per frame. The counter value mayrepresent the slot number (e.g., 1 . . . 64) of the beam hopping frame.Sequential logic 1206 takes the output of timeslot counter 1208 and maygenerate (1) the proper addresses for memory 1204, (2) addresses for thelatches in the BFN modules, and (3) the control signals to place thebeam weights on the data bus. Sequential logic 1206 may then load thisdata into the appropriate latches in beamforming modules 1210, which maybe co-located with, or part of either a BFN 710 or a BWP 714.

Within beamforming modules 1210, data may be double latched to allow allof the beam weights within each beamforming weight vector to change atthe same time. This may ensure hopping of all spot beams synchronouslywith the timeslot boundary. The data may be loaded into the first latchbased on enable signals, which are decoded from the latch address bydecoder 1212, which may be co-located with, or part of either a BFN 710or a BWP 714. Then all data may be simultaneously loaded into thedigital-to-analog (D/A) converters synchronously with a strobe signalfrom the sequential logic. The strobe may be generated within sequentiallogic 1206 to occur at the start of each timeslot.

In the example of FIG. 12, certain components are shown within the BFNmodules. This approach may be advantageous since it may reduce orminimize the number of connections between a BWP 714 and a BFN 710, butother possible implementations may be used. For example, theinterconnect signals may be limited to the 48-bit data bus, the latchaddress bus, plus a strobe line. The 48-bit data bus may enable loadingof 4 complex weights at one time (based on 6 bits for I+6 bits for Q×4weights=48 bits). In this example, there is a total of L=1024 feedelements×K=80 pathways×2 (for Tx and Rx), for a total of 163,840 complexweights. Loading 4 complex beam weights at a time requires 40,960addressable locations, or a 16-bit latch address bus resulting in atotal interconnect of 48+16+1=65 lines.

In some embodiments, the address decoding, latches, and D/As areincorporated in the BWP itself. This may simplify the BFN modules, butsignificantly increase the required number of interconnects. Forexample, using L=1024 elements×K=80 pathways×2 (for Tx and Rx)×2 (I andQ)=327,680 analog voltage (D/A output) lines.

FIGS. 13A through 13C illustrate an example of a communicationssatellite 120 having K=4 pathways, in accordance with aspects of thepresent disclosure.

FIG. 13A shows an illustration 1300 of the payload of the communicationssatellite 120. The instantaneous (e.g., timeslot) signal flow for anexample pathway that conveys traffic that originates in Cleveland(designated Spot Beam 124) and destined is for Pittsburgh (designatedSpot Beam 319) is shown within dashed line 1302. BWP 714-d will set thecoefficients, e.g., as shown in FIG. 8, to the proper values to focusthe LHCP feed elements 128 of the phased array receive antenna assembly121 upon the spot beam coverage area 126 associated with the Clevelandspot beam 125. Terminals, including access node terminals 130 and/oruser terminals 150, within the designated receive spot beam coveragearea 126 will broadcast on the designated uplink frequency through anLHCP antenna. The received version of these signal(s) (e.g., feedelement Rx signals) will be processed and output from the Rx BFN 710-gto pathway 1 and will then go through the pathway processing asdiscussed above. The output from pathway 1 will then be input into theTx BFN 710-i (e.g., feed forming network). BWP 714-d will set thecoefficients (e.g., as described with reference to FIG. 9) to the propervalues to focus the RHCP feed elements 128 of the phased array transmitantenna upon the area designated as the Pittsburgh beam. Terminals,including access node terminals 130 and/or user terminals 150, withinthe designated transmit spot beam coverage area 126 will receive on thedesignated downlink frequency through an RHCP antenna.

From the perspective of the communications satellite 120, uplink signalsare received by the communications satellite 120 from transmitting userterminals 150 or from transmitting access node terminals 130 located inthe satellite's receive service coverage area 410. Downlink signals aretransmitted from the communications satellite 120 to receiving userterminals 150 or to receiving access node terminals 130 located in thesatellite's transmit service coverage area 410. From the perspective ofthe ground equipment (e.g., user terminals 150 and access node terminals130), the receive service coverage area 410 and the transmit servicecoverage area 410 may be reversed.

FIG. 13B shows a configuration table 1310 of the instantaneousconfiguration of the example communications satellite 120. Each rowcorresponds to one pathway. Column 1312 includes the number of thepathway, 1 . . . K. Column 1316 includes

-   -   1. a unique designation of the uplink receive spot beam 125,        which may be an alphanumeric string    -   2. an alphanumeric ‘arrow’ to designate the direction of signal        travel    -   3. the corresponding downlink transmit spot beam 125, which may        also be an alphanumeric string        In these examples, pathways may cross polarizations, in        accordance with typical industry practice. The convention for        the example communications satellites 120 in this document is        that the first K/2 pathways receive LHCP uplink spot beams 125        and transmit RHCP downlink spot beams 125, while the second K/2        pathways receive RHCP uplink spot beams 125 and transmit LHCP        downlink spot beams 125.

FIG. 13C shows an example timeslot coverage area superimposed on areamap 1320. As discussed previously, pathway 1 has an LHCP uplink fromCleveland and an RHCP downlink to Pittsburgh. The communicationssatellite 120 is shown for this pathway, but is omitted for the otherthree pathways shown in this figure. For example, pathway 3 has an RHCPuplink from Washington, D.C. and an LHCP downlink to Columbus and isindicated by a straight line on the figure.

At any timeslot in the beam hopping frame, the forward capacity in eachspot beam 125 can be calculated by performing a link analysis includingthe characteristics of the ground equipment. By performing a standardlink analysis, one can calculate the end-to-endcarrier-to-noise-plus-interference ratio, E_(s)/(N_(o)+I_(o)), to aparticular point in the spot beam coverage area 126. The end-to-endcarrier-to-noise ratio, E_(s)/N_(o), typically includes the effects ofthermal noise, C/I, intermodulation distortion, and other interferenceterms on both the uplink and the downlink. From the resulting end-to-endE_(s)/(N_(o)+I_(o)), the modulation and coding may be selected from awaveform library that maximizes the capacity. An example of a waveformlibrary is contained in the DVB-S2 specification, although any suitablewaveform library may be used. The selected waveform (modulation andcoding) results in a spectral efficiency, measured in bps/Hz, to thatspecific point in the spot beam coverage area 126.

For broadcast data delivery, the spectral efficiency may be computed atthe most disadvantaged point (e.g., at the worst link budget) within thespot beam coverage area 126. For multicast data delivery, the spectralefficiency may be computed at the location of the most disadvantageduser in the multicast group. For unicast data delivery, Adaptive Codingand Modulation (ACM) may be employed, where the data delivered to eachlocation in the spot beam coverage area 126 is individually encoded tofit the link budget for that particular location in the spot beamcoverage area 126. This is also the case with the DVB-S2 standard. WhenACM is employed, the average spectral efficiency is relevant. Asdescribed in U.S. Patent Application Publication No. 2009-0023384 toMark J. Miller, filed Jul. 21, 2008, which is incorporated by referenceherein in its entirety, the average spectral efficiency may be generatedby computing the weighted average of the spectral efficiency for everylocation in the spot beam coverage area 126.

The link capacity in a spot beam 125 may then be calculated as theproduct of the spectral efficiency (bps/Hz) and the allocated BW in thespot beam 125. The total capacity during one timeslot in the beamhopping frame is the sum of capacities of all the spot beams 125 thatare active during that timeslot. The total capacity is the average ofthe capacities of the individual beam hopping frames. To maximize totalcapacity, the beam weights may be set for all spot beams 125 and alltimeslots to yield the largest antenna directivity. Spot beams 125 thatare formed in the same timeslot and use the same polarization andspectrum should be spaced as far apart as possible to maximize the C/I(and hence minimize the interference into other spot beams 125). Underthese requirements, it is not uncommon for the spectral efficiency ofeach spot beam 125 to be approximately the same for all spot beams 125in all timeslots. Under this assumption, the system forward capacity canbe approximated in accordance with:C _(F) =K _(F)·η_(Hz) ·W   (1)where η_(Hz) is the spectral efficiency in bps/Hz, K_(F) is the numberof forward spot beams 125, and W is the spectrum allocated per spot beam125. From equation (1), it can be seen that increasing any of theparameters increases the capacity.

The maximum number of spot beam pairs that can be active at one time,K_(F), is essentially determined by the mass and volume budgets of thecommunications satellite 120. The power limitations on thecommunications satellite 120 can also affect the value K_(F), but thevolume and mass constraints generally are more limiting.

The architecture for providing a satellite communications servicedisclosed herein is effective in maximizing η_(Hz) and W. Due to thesmall size of the spot beams 125, and the relatively small number ofspot beams 125 that can be active at one time (due to payload size,weight, and power limits on K_(F)), all of the allocated spectrum can beused within each spot beam 125 with minimal interference between spotbeams 125. To accomplish this, spot beams 125 of the same polarizationthat are active in the same timeslot should be positioned as far apartas possible. Alternatively, one could use only a fraction of thespectrum per spot beam 125 in order to improve the C/I, but due to thebeam hopping nature of the present architecture this may result in lesscapacity. For example, suppose each spot beam 125 used one-half of theavailable spectrum, or W/2 Hz. Then at any instant in time, there wouldbe half as many spot beams 125 that are co-frequency and present thepotential for interference. The resulting C/I would increase, thusslightly increasing the spectral efficiency, η_(Hz), as C/I is just oneof many components in the end-to-end E_(s)/(N_(o)+I_(o)) budget andspectral efficiency generally varies as the logarithm of theE_(s)/(N_(o)+I_(o)). But the BW per spot beam 125 is reduced by a factorof 2, and as expected, the total capacity will be reduced, since thenumber of spot beams 125 may limited by the number of signal pathways inthe communications satellite 120.

The spectral efficiency per spot beam 125 is quite high using thepresent architecture because active spot beam coverage areas 126 can bespaced far apart and the directivity of the spot beams 125 may be large.The former is a result of the large extents of a service coverage areas410, the small size of spot beams 125, and the relatively small numberof spot beams 125 that can be active at one time. The latter is a resultof the small size of spot beams 125.

In some embodiments, it may also be desirable to increase the spectralefficiency of a spot beam 125 by reducing the associated spot beamcoverage area 126 relative to its beamwidth. Typically, the spot beamcoverage area 126 in spot beam systems may extend out to the −3 dBcontours of a spot beam 125 or beyond. Some systems extend the spot beamcoverage area 126 out to the −6 dB contours. These low contour regionsare undesirable for many reasons. First, they may reduce the downlinkE_(s)/N_(o) and reduce the downlink C/I. The reduced C/I is a result ofthe reduced signal power (C) and the increased interference (I) as thelocations at the edge of a spot beam coverage area 126 are closer toother spot beam coverage areas 126. When computing the weighted averagecapacity (e.g., for unicast data delivery) or the edge of spot beamcapacity (e.g., for broadcast data delivery), this large antenna rolloff at the edge of the spot beam 125 may reduce capacity. In accordancewith the present architecture, however, the spot beam coverage area 126may be constrained to regions within the spot beam 125 where the antennaroll-off is much less, such as approximately −1.5 dB. This may increasethe spectral efficiency since there are no locations in the spot beam125 at the −3 to −6 dB levels relative to beam center. The spot beamcoverage area 126 may be smaller, however, but this is compensated forby hopping to more areas within the beam hopping frame (e.g., increasingthe number of timeslots per frame).

The link capacity may be enhanced by:

-   -   Use of the full allocated spectrum per spot beam 125.    -   Use of small spot beams 125 resulting in high beam directivity        and large uplink E_(s)/N_(o) and ultimately better return link        spectral efficiency.    -   Large service coverage areas 410 realized by hopping small spot        beams 125 around in a beam hopping frame with many slots per        frame resulting in a relatively small number of spot beams 125        active at one time and spread over a large service coverage area        410. Thus, spot beams 125 can be spaced far apart resulting in        high C/I values leading to higher spectral efficiency.    -   Defining smaller spot beam coverage areas 126 such that the edge        of spot beam roll off is relatively small, such as approximately        −1.5 dB. This increases the average spectral efficiency, and the        capacity per spot beam 125, as the relatively high roll-off        locations of spot beam coverage areas 126 that degrade both        uplink C/I and E_(s)/N_(o) have been eliminated.

FIG. 14 illustrates an example process 1400 for supporting satellitecommunication, in accordance with aspects of the present disclosure.Process 1400 may correspond to one pathway (such as the pathway shownwithin dashed line 1302 of FIG. 13A), which can service a forward and/orreturn link of a hub-spoke satellite communication system, such assatellite communications system 100 described with reference to FIG. 1.It should be understood that in practical applications, a large numberof these pathways will be active during a single timeslot dwell time,and thus a corresponding large number of these processes will beoperating in parallel.

At 1402, a current frame is selected. For example, a beam weightprocessor (e.g., BWPs 714 as described with reference to FIG. 7 or10-13) may receive one or more pre-computed weight sets via a data link(e.g., a data link 716 as described with reference to FIG. 7). The frameselected at 1402 may include one or more timeslot definitions and one ormore beamforming weight matrices. For example, the BWP 714 or affiliatedhardware may provide the bulk storage for a plurality of beam hoptimeslot definitions and a plurality of beamforming weight matrices. Abeamforming weight matrix may include the set of all complex beamformingweight vectors used for transmission and reception of all spot beams 125in one timeslot. A beamforming weight vector may include the group ofL_(tx) or L_(rx) individual complex beam weights used for calculationsto/from feed element Tx/Rx signals carried via the feed elements 128 ofa feed array assembly 127 to form one spot beam 125 during one timeslot.A beam hop timeslot definition may include the set of all pathway gainsof all spot beams 125 in one timeslot and may specify all dwell timesassociated with the timeslot.

At 1404, a first timeslot definition and a first beamforming weightmatrix are selected for the current frame. For example, sequential logic(e.g., sequential logic 1306 as described with reference to FIG. 13) ofa BWP may include a counter for selecting a timeslot. Timeslotdefinitions and/or weight matrices may also include location data usedto create one or more receive spot beams 125, one or more transmit spotbeams 125, or both. For example, the location data may include the setof all complex weight vectors used to generate the active spot beams 125for the timeslot.

At 1406, a determination is made whether the communication is part of aforward link or a return link. As explained above, in a hub-spokesystem, an access node terminal (e.g., an access node terminal 130described with reference to FIG. 1) may communicate with user terminals(e.g., user terminals 150 as described with reference to FIG. 1) usingdownstream (e.g., forward) links, while user terminals (e.g., userterminals 150 as described with reference to FIG. 1) may communicationwith an access node terminal 130 using upstream (e.g., return) links.The access node terminal 130 may service its own uplinks and downlinksto and from a communications satellite (e.g., communications satellites120 described with reference to FIGS. 1A through 3D, 7, 10, or 11). Theaccess node terminal 130 may also schedule traffic to and from the userterminals 150. Alternatively, the scheduling may be performed in otherparts of the satellite communications system (e.g., at one or more NOCs,gateway command centers, or other network devices 141). For example, insome embodiments, the gain settings included in the frame definition(e.g., as part of each timeslot definition) may be used to determinewhether a communication is a forward link or a return link.

If, at 1406, a forward link is being processed, then at 1408 the gainfor the pathway may be adjusted, if necessary, to support a forwardlink. For example, a selectable gain channel amplifier may provide thegain setting for the pathway in use, as shown in FIG. 7. The gainsetting can be determined from the first timeslot definition. At 1410, areceive spot beam signal is created for the duration of the timeslotdwell time. For example, a satellite-based receive antenna assembly 121including a receive beamforming network (e.g., BFN 710 a as describedwith reference to FIG. 7) may be configured to create one or morereceive spot beams 125 on the antenna assembly 121 for the duration ofthe timeslot dwell time. The receive spot beams 125 may be used toreceive one or more multiplexed signals (e.g., a multiplexed signal froman access node terminal 130) destined for a plurality of terminals. Forexample, the multiplexed signal may be destined for user terminals 150.At least some of the individual component signals of the multiplexedsignal can differ in content, for example, if destined for differentuser terminals 150. The multiplexed signal may be multiplexed using anysuitable multiplexing scheme, including, for example, MF-TDM, TDM, FDM,OFDM, and CDM. In general, TDM is used for simplicity.

If, at 1406, a return link is being processed, then at 1412 the gain maybe adjusted, if necessary, to support a return link. For example, aselectable gain channel amplifier may provide independent gain settingsfor the pathways in use, as described with reference to FIG. 7. The gainsetting can be determined from the first timeslot definition. At 1414, areceive spot beam signal is created for the duration of the timeslotdwell time. For example, a satellite-based receive phased array antennaassembly 121 including a receive beamforming network (e.g., BFN 710 adescribed with reference to FIG. 4) may be configured to create one ormore receive spot beams on the antenna assembly 121 for the duration ofthe timeslot dwell time. The receive spot beam is used to receive one ormore multiple access composite signals (e.g., a composite signal derivedfrom a plurality of user terminals 150) destined for an access nodeterminal 130. The multiple access composite signal may be formed usingany suitable multiple access scheme, including, for example, MF-TDMA,TDMA, FDMA, OFDMA, and CDMA. The multiple accesses during the slotperiod may be all random access, all scheduled transmissions, or amixture of random access and scheduled transmissions.

At 1416, a satellite-based transmit phased array antenna assembly 121including a transmit beamforming network (e.g., BFN 710-b described withreference to FIG. 7) is configured to generate one Tx spot beam signalfor the duration of the timeslot dwell time. The Tx spot beam signal isderived from the received multiplexed or multiple access compositesignal using a bent-pipe pathway on the satellite. For example, one ormore of frequency conversion, filtering, and selectable gainamplification may be performed on the received signal to create the Txspot beam signal.

At 1418, the timeslot dwell period has passed and a determination ismade whether there exist additional timeslots in the frame definition toprocess. For example, sequential logic (e.g., sequential logic 1306described with reference to FIG. 13) may be instructed to automaticallyloop timeslots included in a frame definition at the conclusion of eachframe. As described above, frame definitions and beamforming weight setsmay be time-varying and dynamically adjusted locally at thecommunications satellite 120 (e.g., by sequential logic 1306 or computer1302 described with reference to FIG. 13), or remotely at a groundfacility using a data link (e.g., a data link 716 as described withreference to FIG. 7). If, at 1418, there are more timeslots to process,then at 1420 the next timeslot may be selected for processing. Forexample, a new timeslot may be selected immediately after the timeslotdwell time of the timeslot selected in 1404 has elapsed. In practice,multiple timeslot definitions and multiple beamforming weight sets maybe loaded into memory (e.g., memory 1204 of BWP 714-c described withreference to FIG. 13) and timeslot definitions and beamforming weightmatrices may be accessed by following a pointer, for example, of alinked list or other data structure. Process 1400 may then return to1406 to create new Rx spot beam signals and generate new Tx spot beamsignals for the new timeslot dwell time. If, at 1418, a determination ismade that there are no more timeslots to process in the frame, then at1419 a determination is made whether or not a new frame definition or anew beamforming weight set has been received. For example, a command tochange frame definitions and/or beamforming weight sets may have beenreceived (e.g., from a computer 1302 as described with reference to FIG.13, or from a remote scheduler) or a new frame definition and/or a newbeamforming weight set may have been uploaded to the communicationssatellite 120. If, at 1419, neither a new frame definition or a newbeamforming weight set has been received, then the current frame may beprocessed again (e.g., automatically repeated). If a new framedefinition or a new beamforming weight set has been received, this newframe definition or this new beamforming weight set may be selected forprocessing.

As an example of the high capacity offered, consider a satellitecommunications system with the following parameters:

-   -   A 5.2 m reflector 122 of an antenna assembly 121 on        communications satellite 120 with a 15 kW power available for        use by the payload.    -   Ka band operation with an allocated spectrum of 1.5 GHz on each        of 2 polarizations.    -   Payload volume and mass constraints support up to 100 pathways,        each 1.5 GHz wide (using all spectrum on one polarization)        active at one time. Assume 50 pathways are used for forward        traffic and 50 pathways for return traffic, yielding a total of        50*1.5 GHz=75 GHz of spectrum in each direction.    -   A 75 cm user terminal 150. For large spacing of spot beam        coverage areas 126 (large service coverage area 410), the        resulting forward link budget supports a spectral efficiency of        about 3 bps/Hz resulting in about 225 Gbps of forward capacity    -   The return link budget supports 1.8 bps/Hz resulting in 135 Gbps        of return link capacity. The total capacity is about 360 Gbps.

As shown in FIG. 7, a communications satellite 120 may contain K genericsets of pathways. Each pathway consists of a formed receive spot beam125 or a formed transmit spot beam 125 which are interconnected by pathelectronics nominally consisting of filters, a downconverter, andamplifiers. In accordance with one embodiment of the subject inventionemploying a hub spoke system architecture, these K pathways can be usedto flexibly and programmably allocate capacity between the forwarddirection (e.g., access node terminal(s) 130 to user terminal(s) 150)and the return direction (e.g., user terminal(s) 150 to access nodeterminal(s) 130). The allocation is flexible in that that the totalresources can be split amongst forward and return in any proportiondesired resulting in any desired ratio between forward and returnchannel capacity. The allocations are programmable in that the splittingof the resources can be altered at every frame, thus rapidly changingthe ratio between forward and return capacity. This is particularlyuseful for changing the forward/return capacity allocation toaccommodate new and evolving applications using data/informationtransfer over a satellite communications system.

The flexible capacity allocation is accomplished by a flexibleallocation of resources in the satellite architecture. The resources ofinterest here are the number of physical pathways on a communicationssatellite 120 and the time fractions in each beam hopping frame. Twoapproaches are presented for flexible capacity allocation. Approach 1flexibly allocates time resources, where approach 2 flexibly allocatesHW resources.

Approach 1: Flexible Allocation of Time Resources

In this approach, one or more pathways are allocated for use in theforward direction a fraction of the time, α_(F). The remainder of thetime (1−α_(F)) it is used for return traffic. Suppose there are Q fixedlength time slots in the beam hopping frame. Then for Q_(F)≈α_(F) Q outof the Q time slots the pathway will be configured for forward traffic.Alternatively, the forward time slots and return time slots could varyin length by the same ratio, although the examples that follow will belimited to the case of fixed length time slots.

Configured for forward traffic means that the Rx spot beam 125 uses abeamforming weight vector that has the Rx spot beam 125 pointed to asite of an access node terminal 130, the Tx spot beam 125 uses abeamforming weight vector that has the Tx spot beam 125 pointed at auser service area (e.g., a Tx spot beam coverage area 126 including oneor more user terminals 150), and the channel amplifier associated withthe pathway is set to yield the satellite net gain that is consistentwith a forward channel. Configured for return traffic means that the Rxspot beam 125 uses a beamforming weight vector that has the Rx spot beam125 pointed to a user service area (e.g., an Rx spot beam coverage area126 including one or more user terminals 150), the Tx spot beam 125 usesa beamforming weight vector that has the Tx spot beam 125 pointed at asite of an access node terminal 130, and the channel amplifierassociated with the pathway is set to yield the satellite net gain thatis consistent with a return channel.

In many, if not most, hub spoke applications the sizes of userterminal(s) 150 and access node terminal(s) 130 are quite different. Forexample, an antenna of an access node terminal 130 might be 7 m indiameter with 100's of Watts of output power capability in the HPAbehind it, and an antenna of a user terminal 150 may be less than 1 m indiameter with only several Watts of output power capability in the HPAbehind it. In such scenarios, it is common for the desired netelectronic gain of one or more antenna assemblies 121 of acommunications satellite 120 to be different in the forward directionfrom the return direction. Thus, in general, the channel amplifier in apathway needs to be configured for different gains in the forward andreturn directions.

In an extreme example, let Q_(F)=Q for all pathways. The result is aForward Link Only (FLO) system in which all capacity is allocated to theforward link and no capacity is allocated to the return link. This isuseful for a media broadcast system, for example. However, the samecommunications satellite 120 can be configured (via uploading adifferent beamforming weight set and channel amplifier gain set) toallocate 75% (for example) of the time slots for forward transmissionand 25% for return transmission. This would result in a forwarddirection capacity of 75% of the FLO example and a return capacity of25% of the maximum of what could be achieved. In general, let C_(F_max)be the forward channel capacity with all time slots allocated to theforward direction and let C_(R_max) be the return channel capacity withall time slots allocated to the return direction. Then for Q_(F) forwardtime slot allocations and Q_(R)=Q-Q_(F) return channel time slotallocations, the forward and return capacity is

$\begin{matrix}{{C_{F} = {{\frac{Q_{F}}{Q} \cdot C_{{F\_}\max}}\mspace{14mu}{and}}}{C_{R} = {\left( {1 - \frac{Q_{F}}{Q}} \right) \cdot C_{{R\_}\max}}}} & (2)\end{matrix}$where Q_(F) can assume any value from 0 (all return traffic) to Q (allforward traffic). It is clear from (2) that the allocation of capacitybetween forward and return can take on any arbitrary proportion limitedonly by the value of Q, the number of time slots per beam hopping frame.For reasonable sizes of Q, such as Q=64, this limitation is not verylimiting as it allows allocation of capacity in increments of 1/64 ofthe maximum value.

In this approach, all K pathways are used exclusively for forwardtraffic or exclusively for return traffic at any instant of time. Therequirements for the total number of locations of access node terminals130 can be determined as follows. Let there be K pathways each using WHz of spectrum on a single polarization. Furthermore, let there beN_(GW) access node terminal sites, each capable of using W Hz ofspectrum on each of two polarizations. At any instant of time, the totaluser link spectrum is KW Hz, which is being used for either forward linkor return link transmissions (but never both). The total feeder linkspectrum utilized at any given instant is 2N_(GW)W, which is also usedfor either forward link transmission or return link transmission, butnever both. Equating the two spectrum quantities results in the requirednumber of access node terminals, N_(GW)=K/2.

This approach is inefficient since an access node terminal 130 is notboth transmitting and receiving 100% of the time. The fraction of timean access node terminal 130 spends transmitting added to the fraction oftime that the access node terminal 130 spends receiving is equal to 1.However, an access node terminal 130 could both transmit and receive100% of the time and is thus being inefficient and underutilized.

Such an approach is said to be synchronized, as illustrated in FIG. 15Awhich shows a 50%-50% time resource allocation 1500 between the forwardand return link for each pathway. The pathways are synchronized in thatthey all service the forward link at some times and all service thereturn link at other times. As can be seen in time resource allocation1500, the total feeder link spectrum used is always KW Hz, and it isalways either all forward link spectrum or all return link spectrum. Asdiscussed above, this synchronized system requires K/2 access nodeterminals 130.

FIG. 15B shows an example synchronized time resource allocation 1510 onan example 8-pathway communications satellite 120 with 8 spot beams 125and 4 access node terminals 130. In Slot 1 of time resource allocation1510, all four access node terminals 130 (e.g., GW1, GW2, GW3 and GW4)are transmitting to spot beams B1-B8 as shown in the slot configurationof the time resource allocation 1510. Below the slots, the pathway (PW)usage of the slot is detailed. In Slot 1, all 8 pathways are used forforward links, thus the entry 8F. In Slot 2, user terminals 150 in allthe spot beam coverage areas 126 are transmitting to their respectiveaccess node terminals 130, so the pathways usage is denoted 8R. To theright of the table, the slot usage is listed for each pathway. For allpathways, the first slot is forward and the second slot is return, soeach slot usage entry is FR.

In this example, the access node terminals 130 may be autonomous fromeach other, although equivalently the transmit access node terminal 130to a user spot beam 125 could be different than the receive access nodeterminal 130 for that user spot beam 125. In that case, the access nodeterminals 130 would need to cooperate in order to provide coherenttwo-way communication to and from user terminals 150. Note that in allsuch synchronized cases, half-duplex (transmit and receive at differenttimes) user terminals 150 could be deployed, as all the user spot beams125 can be scheduled such that the user terminal transmit slots do notoverlap with corresponding receive slots.

The approach can be improved by interleaving the forward and return timeallocations as shown in time resource allocation 1600 of FIG. 16A. Theforward and return time allocations for each pathway are structured suchthat at any instant of time, half of the pathways are used for forwardtraffic and half are used for return traffic. This results in the totalfeeder link spectrum requirement at any instant of time being the same(KW Hz), but it is evenly split between the forward link and the returnlink. Since the example access node terminal 130 has 2 W Hz of spectrumto use in forward direction and 2 W Hz to use in the return direction,the total number of access node terminals 130 required is K/4. This ishalf the number of access node terminals 130 required when synchronizingthe forward and return time allocations, and hence the preferred way tooperate.

FIG. 16B shows an example of a 50%-50% time resource allocation 1610with a similar 8-path communications satellite 120 and 8 spot beams 125as in FIG. 15B. Now, however, only two access nodes are required, GW1and GW2. In FIG. 16B, GW1 is transmitting LHCP to B1 (which receivesRHCP) and transmitting RHCP to B2 (which receives LHCP). Due to theseparate polarization, there is no signal interference between spotbeams 125, even though they are physically adjacent and could evenoverlap partially or totally. At the same time (during that first timeslot), the user terminals in B7 and B8 are transmitting to access nodeterminal GW1. Also during this first time slot of FIG. 16B, access nodeterminal GW2 is transmitting to B3 and B4, while B5 and B6 aretransmitting to access node terminal GW2. In the second slot, as in FIG.15B, the transmission directions are reversed from those of slot 1.Comparing FIG. 16B to FIG. 15B, it can be seen that each spot beam 125has exactly the same number of transmission and reception opportunities.Note that in this specific case, half-duplex user terminals 150 could bedeployed, as the spot beams 125 are scheduled such that the userterminal transmit slots do not overlap with corresponding receive slots.A different schedule could be used that would also achieve the 50%-50%time allocation, but with spot beam transmit and receive slot overlap,possibly requiring that user terminals 150 operate full-duplex, wherethey could transmit and receive at the same time.

In this example, again the access node terminals 130 may be autonomousfrom each other, since each spot beam 125 has a single access nodeterminal 130 for both its forward (to the user spot beam 125) and return(to the access node spot beam 125) transmissions. Also equivalently tothe scenario of FIG. 16B, the transmitting access node terminal 130 to auser spot beam 125 could be different than the receiving access nodeterminal 130 for that user spot beam 125. In that case, the access nodeterminals 130 would need to cooperate in order to provide coherenttwo-way communication to and from user terminals 150.

FIG. 17A shows an example of an interleaved time resource allocation1700 for a 75%-25% time allocation between the forward and returntraffic. In this example, 75% of the pathways are used for forwardtraffic at each instant of time. The remaining 25% are used for returntraffic. Each individual pathway is also used for forward traffic during75% of the beam hopping frame and return traffic during 25% of the beamhopping fame. The result is that at any and every instant of time, theBW used for forward traffic is 3 KW/4 and the BW used for return trafficis KW/4. Since each access node terminal 130 can use 2 W Hz of bandwidthfor forward traffic and 2 W Hz of bandwidth for return traffic, thetotal number of access node terminals 130 required is 3K/8 and islimited by the forward link BW utilization. This number is still smallerthan the K/2 value required for the synchronized approach for a 50%-50%time resource allocation, as shown in FIGS. 15A-B.

FIG. 17B shows the 4 time slots of an example system including the eightspot beams 125 and four access node terminals 130 of FIG. 15B. As inthat example, access node terminals 130 either transmit or receiveduring each slot, but never both transmit and receive in the same slot.The usage summary at the bottom of the configuration table shows thateach slot has 6 forward (e.g., access node terminal to user terminal)pathways and 2 return (user terminal to access node terminal) pathways.

In the first slot, user terminals in B1 and B2 transmit to access nodeterminal GW1, while all other user terminals 150 receive. In the secondslot, the user terminals in B7 and B8 transmit, while the othersreceive. In the third slot, the user terminals 150 in B3 and B4 are theonly ones to transmit, while in the fourth slot, the user terminals 150in B5 and B6 are the only transmitters. Tabulation of the slots willconfirm that each spot beam has 3 forward pathways from a single accessnode terminal 130 to the spot beam 125, and one return pathway from thespot beam 125 to that same access node terminal. In this case, K/2=4access node terminals 130 are used, although the minimum number ofaccess node terminals 130 is 3K/8=3 access node terminals.

If 100% of the traffic were allocated to the forward link, all pathwayswould be used for forward traffic 100% of the time. This would result inthe total forward spectrum of KW Hz and the required number of accessnode terminals 130 would be K/2, the same number as in the synchronizedapproach.

In the general case, each pathway is allocated to be a forward pathwayfor a fraction α_(F) of the time in the beam hopping frame. Theallocations are interleaved with the objective of having a fractionα_(F) of the K total pathways operating as forward pathways at eachinstant of time. The remainder, K(1−α_(F)), would be operating as returnlink pathways. At each instant of time, the required forward linkspectrum is KWα_(F) and the required return link spectrum isKW(1−α_(F)). Hence the total number of required access node terminals130 is N_(Gw)=Max(α_(F), 1−α_(F))K/2. Note this may require coordinationamong the access node terminals 130.

Approach 2: Flexible Allocation of Hardware Resources

In this approach, any single pathway is either dedicated entirely (alltimes slots in the beam hopping frame) to forward link transmissions ordedicated entirely to return link transmissions. What is flexible is thenumber of pathways that are dedicated to forward pathways and the numberof pathways that are dedicated to return pathways. This is illustratedin FIG. 18A for an example allocation of 75% of the pathways to forwardlinks and 25% to return links.

FIG. 18B shows the timeslots for a 75% -25% pathway allocation 4 slotframe for the example 8 pathway communications satellite 120 asdiscussed previously. Here, the pathways are identified by number in themap view. Pathway 1 (LHCP→RHCP) and Pathway 5 (RHCP→LHCP) are dedicatedto return traffic, while the remaining pathways are dedicated to forwardtraffic.

In slot 1, access node terminal GW 1 receives data from spot beams B1and B2, while all three access node terminals transmit to the remainingspot beams. In slot 2, spot beams B3 and B4 transmit to access nodeterminal GW1, while all three access node terminals transmit to theremaining spot beams. In slot 3, spot beams B5 and B6 transmit to accessnode terminal GW1, while all three access node terminals transmit to theremaining spot beams. In slot 4, spot beams B7 and B8 transmit to accessnode terminal GW1, while all three access node terminals transmit to theremaining spot beams.

Consider one polarization of this example two-pole system. This systemstill uses three access node terminals, GW1-GW3 (each operating in oneof the two available polarizations), but now only consider spot beamsB1-B4 and pathways 1-4. There are still 4 slots per frame and thus 4pathways×4 slots=16 total slots available. This system has allocated 75%(12) of these slots to forward traffic and 25% (4) of these slots toreturn traffic. The 4 return slots fill the entire frame exactly. The 12forward slots need to be distributed across the 4 spot beams, so eachspot beam gets 3 slots. These same 12 forward slots, however, need to bedistributed across 3 access node terminals, so each access node terminalmust fill 4 forward slots. Thus, there cannot be a one-to-one mappingbetween access node terminals and spot beams such that all the trafficfor any spot beam passes through the same access node.

Careful attention to the number of spot beams 125, slots, access nodeterminals 130, and pathways can provide flexibility in the mapping ofaccess node terminals 130 to spot beams 125. FIGS. 18C-18E show two moreexample embodiments of flexible allocation of hardware resources. Here,there are 6 spot beams that require a 75%-25% pathway allocation in theexample communication system having an 8 pathway satellite and 3 accessnode terminals as discussed previously. Since there are only 6 spotbeams B1-B6, only 3 time slots are required. The user terminals 150 willgenerally operate in full-duplex (simultaneous receive and transmit)mode during their active beam hopping time slots. Now there are 4pathways×3 slots=12 slots to be allocated per polarity. 75% of 12 (9)slots are used for forward traffic, while 25% of 12 (3) slots are usedfor return traffic. The 3 return slots again fill one frame,corresponding to the one pathway allocated for return traffic perpolarity. Now, however, the 9 forward slots (3 per pathway) perpolarization can be divided such that there are exactly 3 slots peraccess node terminal and 3 slots per spot beam, thus allowing aone-to-one mapping between user spot beams and access node terminals.

In FIGS. 18C and 18D, both polarizations are depicted. Forward pathways2-4 and 6-8 are each dedicated to a single access node terminal 130:pathways 2 and 6 (for the two polarizations) of GW 2, pathways 3 and 7for GW 3 and pathways 4 and 8 for GW 1. In FIG. 18C, the return pathwaysare shared among the three access node terminals 130 such that eachaccess node terminal 130 receives from the same spot beam coverage areas126 to which it transmits, thus implementing a one-to-one mappingbetween user spot beams 125 and the access node terminals 130 thatservice them. Alternatively, in FIG. 18D, the return pathways are alldirected to GW 1. In this case, GW 1 is considered a shared receiveaccess node terminal 130 and GW 2 and GW 3 can operate half-duplex astransmit only. In this shared receive access node terminal embodiment, anumber of access node terminals 130 transmit to a number of userterminals 150, while those user terminals 150 only transmit (if theytransmit at all) to a single access node terminal 130, typically one ofthe transmit access node terminals 130. FIG. 18E shows the first timeslot of the system of either FIG. 18C or FIG. 18D, as it is the same inboth cases.

A shared receive access node terminal 130 can have utility, for example,if there are user terminals 150 that transmit requests for informationthat is located at one access node terminal 130, or if one access nodeterminal 130 is the interface between the ground network of access nodeterminals 130 and a network 140. In this case, having all user terminals150 request the information directly from that access node terminal 130will avoid the problem of having the other access node terminal 130forward requests to that interface access node terminal 130.

The reverse is also possible: a shared transmit access node terminalsystem where user terminals 150, perhaps sensor terminals, transmit alarge amount of information, but only need to receive a small amount.For example, a 25%-75% time allocation could be implemented by switchingthe direction of the spot beams 125 in FIG. 15B. Thus, access nodeterminal GW1 would be the common transmitter for all the user spot beams125. In these shared access node terminal embodiments, half-duplexaccess node terminals 130 can be deployed if the system operator has abackbone network (e.g., an example of a network 140 as described withreference to FIG. 1) that connects the access node terminals 130 suchthat traffic can be directed and scheduled properly.

Let K_(F) be the number of forward pathways and K_(R) be the number ofreturn pathways where K_(F)+K_(R)=K is the total number of pathways.Since each pathway is always used entirely in the forward or returndirection, there is no need to dynamically change the net electronicgain through the pathway on a time slot by time slot basis. Hence,dynamic adjustment of the channel amplifier gain on a slot-by-slot basismay not be required.

By setting K_(F)=K and K_(R)=0, we have all forward traffic, (FLO). Bysetting K_(R)=K and K_(F)=0, we have all return traffic, (Return LinkOnly or RLO). In general, the capacity allocation is each direction is,

$\begin{matrix}{{C_{F} = {{\frac{K_{F}}{K} \cdot C_{{F\_}\max}}\mspace{14mu}{and}}}{C_{R} = {{\frac{K_{R}}{K} \cdot C_{{R\_}\max}} = {\left( {1 - \frac{K_{F}}{K}} \right) \cdot C_{{R\_}\max}}}}} & (3)\end{matrix}$where K_(F) can assume any value from 0 (all return traffic) to K (allforward traffic). It is clear from (3) that the allocation of capacitybetween forward and return can be take on any arbitrary proportionlimited only by the value of K, the number of pathways (e.g., of acommunications satellite 120, or of a GBBF system). For reasonable sizesof K, such as K=100, this limitation is not very limiting as it allowsallocation of capacity in increments of 1/100 of the maximum value.

In this approach, at any instant of time the total user link spectrumused in the forward direction is K_(F)W. In the return direction, thetotal spectrum used is K_(R)W. Again, it is assumed that each accessnode terminal 130 has W Hz available for use on each of twopolarizations. The total feeder link spectrum available for use is2N_(GW)W in each direction (forward and return). Therefore the number ofcooperating (not autonomous) access node terminals 130 required is,N_(GW)=Max(K_(F),K_(R))/2, which is the same as approach one whencareful assignment of the Transmit and Receive slots was chosen tominimize the access node terminal count. However, approach 2 has theadvantage of not needing to dynamically change the net gain of thepathway during the beam hopping frame to accommodate dynamic changingbetween forward and return configurations.

FIG. 19 shows an illustrative chart 1900 of the number of cooperatingaccess node terminals 130 (e.g., gateways) required versus the number offorward pathways allocated when K=100. As shown in FIG. 19, the numberof cooperating access node terminals 130 required is minimum whenK_(F)=K_(R), while the number of cooperating access node terminals 130required is maximum for RLO (i.e., K_(F)=0) and FLO (i.e., K_(R)=0).

In all of the discussed approaches, it should be clear that the forwardlink and return link can be operated as two independent transmissionsystems. The allocation of capacity between the two transmission systemscan be divided up in nearly any proportion desired, as possibly limitedby K or Q. Then each transmission system can independently spread itscapacity around a service coverage area 410 in any way desired byappropriate setting of the beamforming weight vectors that create thespot beams 125 in each time slot. Generally, one would set the servicecoverage area 410 for the forward link and return links to be the samephysical area. This provides every point in the service coverage area410 with opportunities for reception of forward link data andtransmission of return link data. In general, these opportunities willnot always occur in the same time slots. It can also be seen that theratio of forward to return traffic need not be the same at every pointin the service coverage area 410. This allows the ratio of forward toreturn traffic to be customized in each spot beam coverage area 126. Themechanism for customizing this ratio is the adjustment of the number(and/or size) of forward and receive time slots allocated to eachphysical location of spot beam coverage areas 126.

FIG. 20A illustrates an example 2000 of non-congruent service coverageareas 410 for forward and return link service, according to aspects ofthe present disclosure. The forward link service coverage area 410-b isthe union of the spot beam coverage areas 126 of the individual forwardlink spot beams 125 formed during a beam hopping time frame. Likewise,the return link service coverage area 410-c is the union of the spotbeam coverage areas 126 of the individual return link spot beams 125formed during a beam hopping time frame. The union of the forward linkservice coverage area 410-b and the return link service coverage area410-c can be broken into 3 regions. Region 1 is the area where thebeamforming weight set provides forward link spot beams 125 but noreturn link spot beams 125. This region could support forward linktraffic only. Region 2 is the area where the beamforming weight setprovides return link spot beams 125 but not forward link spot beams 125.This region could support return link traffic but not forward linktraffic. Region 3 is the region where the beamforming weight setprovides both forward and return spot beams 125, although notnecessarily in the same time slot. Both forward and return link trafficcan be supported. Furthermore, the ratio of forward to return capacitycan be customized in each physical location of spot beam coverage areas126 within region 3.

FIG. 20B illustrates a simple single access node terminal, 4 pathwaysystem, in accordance with aspects of the present disclosure. Here,forward link Region 1 contains spot beams 1 and 2, return link Region 2contains spot beams 5 and 6, while bi-directional Region 3 contains spotbeams 3, 4, 7 and 8. This illustrates that while Region 3 was shown inFIG. 20A as a single logical zone, there is no requirement that the spotbeams 125 comprising Region 3 be contiguous. In fact, Regions 1 and 2,shown in this example as contiguous, could also have been comprised of anumber of distinct areas.

In Slot 1, the access node terminal GW transmits to the terminals inRegion 1, spot beam coverage areas B1 and B2, and receives from theterminals in Region 2, spot beam coverage areas B5 and B6. The terminalsin Region 3 are inactive during this slot, while the terminals inRegions 1 and 2 are inactive during the remaining slots. In Slot 2, theaccess node terminal GW transmits to terminals in spot beam coverageareas B3 and B4 and receives from terminals in spot beam coverage areasB7 and B8. In Slot 3, the access node terminal GW receives fromterminals in spot beam coverage areas B3 and B4 and transmits toterminals in spot beam coverage areas B7 and B8.

The present invention provides a flexible high-capacity satellitecommunications architecture. Characteristics of this architecture mayinclude one or more of the following:

-   -   1. high capacity;    -   2. flexible allocation between forward and return capacity;    -   3. flexible capacity distribution and service coverage areas        410;    -   4. re-configurable service coverage areas 410 and capacity        allocation;    -   5. flexible locations for access node terminals 130, for        example, using beam hopping to enable access node terminals 130        to occupy the same spectrum and the same location as spot beams        125; and the ability to move access node terminal locations over        the lifetime of the satellite;    -   6. incremental rollout of access node terminals 130;    -   7. orbital position independence;    -   8. dynamic equivalent isotropically radiated power (EIRP)        allocation across access node terminals 130 to mitigate rain        fade, for example, where margin requirements are based on a sum        of rain fade on all diverse paths rather than on statistics of        an individual path;    -   9. operation with half-duplex terminals; and    -   10. operation with reduced redundancy payload hardware.        Characteristics (1) and (2) have been described. Further details        of characteristics (3) through (10) are provided below.

A small number of cells can be active at any instant of time, where acell may refer to a portion of a service coverage area 410 (e.g., spotbeam) providing a communications service to a subset of terminals, forexample. In one example, K_(F)=40 to 60 transmit spot beams 125 (e.g.,for user terminal downlink). Beamforming weight vectors can bedynamically changed per an uploaded schedule. Take an example where thetotal number of user cells equals K_(F)×Q, where Q=number of timeslotsand 1≤Q≤64. Here, the composite of spot beam coverage areas 126 isincreased by a factor of Q. The average duty cycle of a spot beam 125may be equal to 1/Q. The forward link speed to a spot beam 125 isreduced by a factor of Q. It may be preferable for a user terminal 150to be able to demodulate all carriers in the W Hz bandwidth. For W=1500MHz, η_(Hz)=3 bps/Hz, and Q=16, the average downlink speed to a userterminal 150 is about 281 Mbps.

Turning to the return link, in one example, K_(R)=40 to 60 receive spotbeams 125 (e.g., for user terminal uplink). Beamforming weight vectorscan be dynamically changed per an uploaded schedule. Take an examplewhere the total number of user cells equals K_(R)×Q, where Q=number oftimeslots and 1≤Q≤64. Here, the composite of spot beam coverage areas126 is increased by a factor of Q. The average duty cycle of a spot beammay be equal to 1/Q. The return link speed to a spot beam 125 is reducedby a factor of Q. It may be preferable for a user terminal 150 to use aburst HPA capable of high peak power but lower average power. For 12 Wpeak HPA with 3 W average power limit, 40 Msps uplink, 2.25 bits/sym,and Q=16, the average uplink speed from a user terminal 150 is 5.625Mbps.

The flexible high-capacity satellite communications architecturedescribed herein may also provide non-uniform distribution of capacityaround a service coverage area 410. Capacity can be allocated todifferent cells in near arbitrary proportions by assigned differingnumbers of slots per cell. Again, there are Q timeslots in a beamhopping frame. Each cell uses q_(j) timeslots, such that

$\begin{matrix}{{\sum\limits_{j = 1}^{J}\; q_{j}} = Q} & (4)\end{matrix}$where J is the number of service beam coverage area locations that aspot beam signal pathway hops to in the beam hopping frame. Capacity ineach cell is:

$\begin{matrix}{C_{j} = {C_{b}\frac{q_{j}}{Q}}} & (5)\end{matrix}$where the instantaneous capacity per spot beam=C_(b).

FIGS. 21A-21C illustrate an example of beam hopping with non-uniformdistribution of capacity, in accordance with aspects of the presentdisclosure. FIG. 21A shows an illustrative beam hop pattern 2100 of asingle spot beam signal pathway for 8 non-uniform timeslot dwell timesof a beam hopping frame. In the example, Q=32 and C_(b)=4.5 Gbps. Thecell locations in the beam hop pattern 2100 are shown as contiguous forease of illustration. FIG. 21B shows an illustrative timeslot dwell timetable 2110 for the beam hop pattern 2100. For each of the 8 timeslotdwell times of the timeslot dwell time table 2110, the number oftimeslots q_(j) assigned to the corresponding cell location and the areacapacity C_(j) in Mbps is shown. FIG. 21C shows an illustrative beamhopping frame 2120 for the timeslot dwell time table 2110. The beamhopping frame 2120 includes K spot beams 125. The non-uniform timeslotdwell times for spot beam #1 of the beam hopping frame 2120 match thedwell times illustrated in the timeslot dwell time table 2110. It ispreferable to have all the spot beams 125 change locations at the sametime. This minimizes the beam-beam interference as each spot beam 125only overlaps in time with K-1 other spot beams 125. However, the systemcan operate without this constraint. More spot beams 125 can theninterfere with each other, and the spot beam locations should be chosenwith this in mind.

Spot beam locations are defined by the weight vectors used in the BFNs710. Capacity per cell is set by the duration of the beam hopping framethe spot beam 125 stays pointed at a cell (dwell time). Both beam weightvectors and dwell times (e.g., as beam hop frame definitions) can bestored in a BWP 714. These values can be uploaded to the BWP 714 by adata link from the ground. Both the beam locations (e.g., spot beamcoverage areas 126) and dwell time (capacity allocation) can be changed.For example, the beam locations and/or the dwell times can be changedoccasionally by uploading new weight sets and new beam hop framedefinitions, or frequently in response to daily variations (e.g.,capacity shifting to match the busy hour) by commanding the BWP 714 touse one of several pre-stored weight sets and beam hop framedefinitions. One beamforming weight set contains beam weights and onebeam hop frame definition contains dwell times for all the beams in alltime slots in a beam hopping frame.

Access node terminals 130 can be placed outside of a user terminalservice coverage area 410, or in a user terminal service coverage area410 at the cost of a small increase in the number of access nodeterminals 130. To facilitate mapping access node terminal locations, onecan use the number of colors available from the access node terminals130. The total number of colors=time colors×polarizationcolors×frequency colors. Take an example with Q=4, W=1500 MHz (fullband), and dual polarization. The total number of colors=4 times×2poles×1 frequency=8. The number of access node terminals 130, N_(GW), isdetermined by

$\begin{matrix}{{{\sum\limits_{i = 1}^{N_{GW}}\; C_{i}} \geq {K \cdot Q}} = {M = {\#\mspace{14mu}{of}\mspace{14mu}{user}\mspace{14mu}{beams}}}} & (6)\end{matrix}$where C_(i)=the number of colors serviceable by access node terminals#i.

FIG. 22A shows illustrative access node terminal locations and user spotbeam coverage area locations for an example with 23 access nodeterminals 130 (22 operational access node terminals+1 utility accessnode terminal). The user spot beam coverage area locations are shown ascells and the access node terminal locations are shown as dashed circlesin the map 2200 of FIG. 22A.

FIG. 22B shows an illustrative access node terminal table 2210 for themap 2200. The access node terminal table 2210 shows, for each accessnode terminal 130, the access node terminal location, the number of spotbeam issues (i.e., the number of colors unusable), and the number ofcolors serviceable by the access node terminal 130, C_(i). For K=40,Q=4, M=160 spot beams, and the C_(i) illustrated in the access nodeterminal table 2210, ΣC_(i)=168≥160. Thus, for this example, the systemcan operate with any 22 out of the 23 access node terminals 130. Placingall the access node terminals 130 with no spot beam infringements wouldrequire K/2=20 access node terminals 130. In this example, only 2additional access node terminals 130 are required to allow some spatialoverlay between access node terminals 130 and user spot beam coverageareas 126.

In an extreme example, all the access node terminals 130 are located inthe user terminal service coverage area 410. Here, K=40, Q=24, and M=960spot beams 125 for full CONUS coverage and a hop dwell= 1/24th of thebeam hopping frame for all spot beams 125. The total number of colors is48=24 times×2 poles. If the access node terminals 130 were located awayfrom the user terminal service coverage area 410, the minimum number ofaccess node terminals 130 would be 20. However, for this extreme examplewith all access node terminals 130 located in the user terminal servicecoverage area 410, the maximum number of colors unusable is assumed tobe 7. Thus, C_(i)≥41=48−7 for all access node terminals 130. It isfurther assumed that 6 access node terminals 130 are located where thenumber of unusable colors is ≤4 (e.g., service coverage area boundariessuch as coastal regions). For these 6 access node terminals 130,C_(i)=48−4=44. The number of access node terminals 130 required is equalto 23, where ΣC_(i)=(6×44)+(17×41)=961≥960. This results in a 15%increase (i.e., from 20 to 23) in access node terminals 130 required,but with complete flexibility in the location of 17 out of 23 accessnode terminals 130, all of which are within the user terminal servicecoverage area 410.

Flexibility in access node terminal locations can also be achieved withnon-uniform hop dwell times. The number of access node terminals 130required is defined by a similar equation

$\begin{matrix}{{\sum\limits_{j = 1}^{N_{GW}}\; C_{j}} \geq {K \cdot Q}} & (7)\end{matrix}$where C_(j)=total number of useable hop dwell periods by access nodeterminal j. The maximum possible value of C_(j) is 2Q (i.e., 2polarization colors, 1 frequency color). The optimum placement of accessnode terminal s is, first, in regions of no service (i.e., C_(j)=maximumvalue), and second, in cells of low hop dwell time and next to cells oflow hop dwell time. Placing access node terminals 130 accordingly willgenerally result in even fewer additional access node terminals 130,compared to the examples above where the hop dwell times are uniform.

FIG. 22C shows illustrative placements 2220 of access node terminals130. In this example, Q=32 hop dwells per beam hopping frame, there are2 polarization colors, and 1 frequency color. The first placement, whereC_(j)=64=maximum value, places the access node terminal 130 in a regionof no user terminal service. The other three placements, where C_(j)<64,place the access node terminals 130 in cells of low hop dwell time andnext to cells of low hop dwell time.

Incremental rollout for access node terminals 130 is described for anexample system with K=40, Q=4, and N_(GW)=20. The number of spot beamsM=160, and the average duty cycle=1/Q=25%. In a first example, ifservice is started with one access node terminal (K=2 pathways), oneaccess node terminal services two beams at a time. Setting the number oftime slots Q=80 provides all 160 spot beams 125. However, the resultingduty cycle= 1/80. Thus, in this first example, there is a reduction inspeed and capacity. The duty cycle can be increased as the number ofaccess node terminals 130 increase.

In a second example, if service is started with four access nodeterminals 130 and only 40 spot beams 125, the resulting service coveragearea 410 is 25% of the initial service coverage area 410. Note that itcan be any 25%. With K=8 pathways, setting Q=5 provides 40 beams, with aduty cycle=⅕. Thus, in this second example, there is minimal reductionin speed and spot beam capacity. The service coverage area 410 can beincreased as the number of access node terminals 130 increase. Theseapproaches trade off initial service coverage area 410 and/orspeed/capacity for a reduced number of initial access node terminals130.

Beamforming weight vectors, and thus locations of spot beam coverageareas 126, are flexible in the satellite communications architecturedescribed herein. Supporting a communications service after a change ofan orbital position can be accomplished by updating (e.g., uploading) anew set of beamforming weight vectors to allow coverage of the same spotbeam coverage areas 126 from a different orbit position. This providesseveral benefits. The orbital position can be undefined at the time thecommunications satellite 120 is being built. The orbital position can bechanged at any time during the lifetime of the communications satellite120. A generic design for a communications satellite 120 can be used forany orbital position and any definition of a service coverage area 410within the reasonable scan range of the reflector 122. Furthermore, anative antenna pattern coverage area 221 for an antenna assembly 121 maybe adapted for such changes in orbital position, as described herein.

Updates to a beamforming weight set for providing a communicationsservice at a new orbital position may be accomplished in variousmanners. In some examples, new beamforming weight sets may be uploadedto a communications satellite 120, or new beamforming weight sets may beselected from those stored at the communications satellite 120. In someexamples, a new beamforming weight set may be received from a networkdevice 141, such as a network management entity. In some examples, a newbeamforming weight set may be calculated at a communications satellite120, based at least in part on the new orbital position of thecommunications satellite. In some examples BFNs 710 may be located at aground segment 102 (e.g., for GBBF), in which case beamforming weightsets may be selected and/or calculated at the ground segment 110.

The updated beamforming weight sets may provide various characteristicsof a communications service at the new orbital position. For example,the beamforming weight sets may be configured in a manner that uses thesame, or a different plurality of feed elements to form a particularspot beam 125, and/or to provide the communications service to aparticular cell. In some examples the beamforming weight sets may beupdated to provide spot beams having the same spot beam coverage area atan updated orbital position. In some examples the beamforming weightsets may be updated to provide sesame service coverage area at anupdated orbital position. In some examples a communications service maybe provided to a plurality of cells of a service coverage area, and inresponse to the change in orbital position, the communications servicemay be provided to at least one of the cells via a spot beam having thesame bandwidth, the same frequency, the same polarization, and/or thesame timing slot sequence as a spot beam from the prior orbitalposition.

In a beamformed Tx system, it is very easy to allocate Tx power to eachaccess node terminal spot beam 125 in a non-uniform and dynamic manner.Tx power to a spot beam 125 is proportional to the sum of the magnitudesquared of the beam weights. Scaling the beam weights up or down willincrease or decrease the power to the spot beam 125. Power can also beadjusted via the channel amplifier attenuation.

Power can be allocated to each access node terminal spot beam 125 ininverse proportion to the rain fade attenuation. This allocation can bedynamic based on the actual rain fade attenuation, or static based onthe rain fade that is associated with a particular availability.

In one embodiment, transmit power is allocated to access node terminals130 based on downlink SNR. For N_(GW) access node terminals 130, thetotal Tx power P_(GW) on the communications satellite 120 (e.g., thetransmitting antenna assembly 121) that is allocated to transmissions tothe access node terminals 130 is

$\begin{matrix}{{\sum\limits_{n = 1}^{N_{GW}}\; P_{n}} = P_{GW}} & (8)\end{matrix}$where P_(n)=Tx power allocated to access node terminal number n. Theproper power allocation to equalize downlink SNR is

$\begin{matrix}{P_{n} = {P_{GW} \cdot \frac{L_{n}R_{n}}{D_{n}} \cdot \frac{1}{\sum\limits_{i = 1}^{N_{GW}}\;\frac{L_{i}R_{i}}{D_{i}}}}} & (9)\end{matrix}$where R_(n)=antenna assembly gain to access node terminal number n;D_(n)=downlink SNR degradation due to rain attenuation at access nodeterminal number n; and L_(n)=free-space path loss to access nodeterminal number n.

In a static approach, power allocations can be selected based on rainattenuation at the target link availability. These fixed powerallocations can be determined by the network planner prior to networkoperation. The rain attenuation, A_(n), can be determined at each accessnode terminal 130 that corresponds to the desired availability. The raindegradation, D_(n), can be calculated from A_(n) and the access nodeterminal HW parameters. The free-space path loss, Ln (e.g., signalpropagation loss), can be calculated to each access node terminal 130.The Tx antenna assembly gain to each access node terminal, R_(n), can bedetermined from the beam weights and native feed element patterns 210.The allocated powers, P_(n), and the required channel amplitudeattenuation setting can be calculated to produce those powers.

The channel amplitude attenuator setting can be sent via uplink to thecommunications satellite 120 and kept at that setting until (and if) onedesires to change the network operation concept (e.g., access nodeterminal locations, downlink availability, total power allocated to theaccess node terminal downlink etc.).

In a dynamic approach, the power allocations can be selected based onthe observed rain attenuation at each access node terminal 130. The Txpower settings, P_(n), will change dynamically as the rain attenuationschanges. In some embodiments, a rain attenuation measurement system isused, and a central processing site (e.g., an NOC, or other networkdevice 141) to gather all the measured rain attenuations, dynamicallycompute the power allocations, and send uplink the power allocation(e.g., as a channel amplitude gain or a beam weight vector) informationto the satellite. FIG. 23 is a simplified diagram of an illustrativesatellite communications system 2300 that can support this dynamicapproach.

In another embodiment, transmit power is allocated to access nodeterminals 130 based on signal-to-interference-and-noise ratio (SINR).For access node terminal downlinks that have relatively high spot beaminterference, it may be preferable to allocate power with an objectiveto equalize downlink SINR.

Both the static approach and the dynamic approach can accommodate thisby using a different equation to calculate the power allocations. Herethe power allocations arex=[R _(gw) C−λGC(R−R _(gw))]⁻¹ λDg   (10)where λ is chosen to force the equality

$\begin{matrix}{{\sum\limits_{n = 1}^{N}\; x_{n}} = P_{GW}} & (11)\end{matrix}$and the below definitions apply.

-   -   x: An N×1 column vector, which contains the Tx power allocations        to each access node terminal 130.    -   R: An N×N beam gain matrix. The component R_(ij) is the gain of        the spot beam pointed at access node terminal j in the direction        of access node terminal i. The diagonal component r_(ii) is the        antenna gain for access node terminal i.    -   R_(gw): An N×N diagonal matrix containing the gain to access        node terminal n. The diagonal elements of R_(gw)=the diagonal        elements of R.    -   D: An N×N diagonal matrix whose elements contain the rain        degradation of each access node terminal. This is calculated        from the measured values of A_(n).    -   C: An N×N diagonal matrix whose elements contain the link        constants of each access node terminal. Specifically,

$\begin{matrix}{{C = {{Diag}\left\lbrack c_{n} \right\rbrack}}{where}{c_{n} = {\frac{G}{T}{(n) \cdot \frac{1}{L_{p}(n)} \cdot \frac{1 + \alpha}{kW}}}}} & (12)\end{matrix}$

-   -   G: An N×N diagonal matrix whose diagonal elements contain the        target relative downlink SINRs for each access node terminal. If        it is desired for all access node terminals to have the same        downlink SINR, then G=the N×N identity matrix.    -   g: An N×1 column vector whose elements are the same as the        diagonal elements of G.    -   λ: A free scalar parameter that must be chosen such that the        power allocations, x_(n), sum up to the total allocated access        node terminal Tx power, P_(GW).        Equation (10) can be solved with an iterative technique.

Thus, as described herein, a satellite communications service may beprovided by a communications satellite 120 that supports beamformed spotbeams 125, which may further support spot beam coverage area locationsthat change according to a beam hopping configuration. Beamformed spotbeams 125 may be flexibly formed by applying beam weights to signalscarried via antenna feed elements 128, which leverage constructive anddestructive effects of electromagnetic signals propagating via aplurality of native feed element patterns 210 of a native antennapattern 220. Flexibility of providing the communications service may befurther improved with a communications satellite 120 that employs one ormore antenna assemblies 121 that support a change in native antennapattern 220.

FIGS. 24A and 24B illustrate a change in native antenna pattern coverageareas 221-d that may be supported by an antenna assembly 121, inaccordance with aspects of the present disclosure. The change in nativeantenna pattern coverage areas 221-d may be provided by commanding anactuator that is included in a feed array assembly 127, included in areflector 122, coupled between a feed array assembly 127 and a reflector122, coupled between two reflectors 122, and so on. For example, anantenna assembly 121 may support a change from native antenna patterncoverage area 221-d-1 to native antenna pattern coverage area 221-d-2 byadjusting a relative position between a feed array assembly 127 and areflector 122 of the antenna assembly 121 as described herein. Thechange in relative position may be provided by a linear actuator 124,and may support, for example, different native antenna patterns 220 forproviding flexible beamforming of a communications service to a servicecoverage area (e.g., service coverage area 410 as described withreference to FIG. 4.).

FIG. 24A illustrates an example diagram 2400 of an native antennapattern coverage area 221-d-1 formed by a plurality of native feedelement pattern coverage areas 211. In some examples the native antennapattern coverage area 221-d-1 may have been intended to support aservice coverage area such as the service coverage area 410 describedwith reference to FIG. 4. In an example, the native antenna patterncoverage area 221-d-1 may be used to provide a communication service tothe service coverage area 410 according to particular conditions of acommunications service. However, it may be desired to change theconditions of the communications service for various reasons. Forexample, the demand profile within a service coverage area 410 maychange, the desired service coverage area 410 may change, an orbitalposition of a communications satellite 120 may have changed, or it maybe desired to change the characteristics of spot beams 125 formed by theassociated native antenna pattern 220-d.

The characteristics of spot beams 125 may be a result of the nativeantenna pattern coverage area 221-d-1 and different beam weights. Forexample, diagram 2400 illustrates an area of interest 2424 in thevicinity of Chicago, Ill. To support area of interest 2424, acommunications satellite 120 may apply beamforming techniques to antennafeed elements 128 of a feed array assembly 127 that are associated withnative feed element pattern coverage areas 211 that enclose the area ofinterest 2442. According to diagram 2400, the native antenna patterncoverage area 221-d-1 includes 8 native feed element pattern coverageareas 211 that enclose the area of interest 2424, as indicated withdark, solid lines. Accordingly, the communications satellite 120 mayemploy 8 antenna feed elements 128 of a feed array assembly 127 tosupport a communications service at the area of interest 2424.

FIG. 24B illustrates an example diagram 2450 of an native antennapattern coverage area 221-d-2 formed by a plurality of native feedelement pattern coverage areas 211, which may be associated with thesame antenna feed elements 128 of the native feed element patterncoverage areas 211 of native antenna pattern coverage area 221-d-1.However, the native antenna pattern coverage area 221-d-2 may havenative feed element pattern coverage areas 211 with differentcharacteristics (e.g., larger native feed element pattern coverage areasize, higher degree of overlap of native feed element pattern coverageareas, etc.) than native antenna pattern coverage area 221-d-1. Thechange from native antenna pattern coverage area 221-d-1 to nativeantenna pattern coverage area 221-d-2 may be provided by commanding anactuator 124 to change a relative distance between a feed array assembly127 and a reflector 122. For example, the native antenna patterncoverage area 221-d-2 of diagram 2450 may represent a feed arrayassembly 127 being located nearer to a reflector 122 than in diagram2400, which may cause a more heavily defocused condition.

As illustrated by diagram 2450, the adjustment of an actuator 124 mayprovide broader native antenna pattern coverage area 221-d-2, ascompared with native antenna pattern coverage area 221-d-1. Bybroadening the native antenna pattern, native antenna pattern coveragearea 221-d-2 may be able to support a broader service coverage area 410,and/or provide a communications service in a service coverage areaaccording to a different coverage area condition (e.g., different spotbeam pattern, spot beam size, spot beam gain, etc.).

For example, the native antenna pattern coverage area 221-d-2 may alsosupport the area of interest 2424 in the vicinity of Chicago, Ill., butaccording to different native antenna pattern coverage areas 221-d. Asillustrated in example diagram 2450, the native antenna pattern coveragearea 221-d-2 includes 11 native feed element pattern coverage areas 211that enclose the area of interest 2424, as indicated with dark, solidlines. Accordingly, the communications satellite 120 may employ 11antenna feed elements 128 of the feed array assembly 127 to support acommunications service at the area of interest 2424. As compared tonative antenna pattern coverage area 221-d-1, the greater number ofantenna feed elements 128 that may be used in native antenna patterncoverage area 221-d-2 to support a communications service at area ofinterest 2424 may improve various aspects of the communications service,such as feed redundancy, signal quality characteristics (e.g., higherbeam gain, different beam gain profile, etc.), and utilization oforthogonal communications resources. Thus, the service coverage area410, including area of interest 2424, may be provided a communicationsservice using a change from native antenna pattern coverage area 221-d-1to native antenna pattern coverage area 221-d-1 and a differentbeamforming weight matrix (e.g., with different beam weights and/ordifferent numbers of feed elements 128 used to support a givenbeamformed spot beam 125).

Although providing the transition from native antenna pattern coveragearea 221-d-1 to native antenna pattern coverage area 221-d-2 bycommanding an antenna assembly 121 to transition to a more defocusedposition may be desirable in some circumstances, in some circumstancesit may be desirable to command an antenna assembly 121 to transition toa more focused position. Thus, commanding an actuator to provide achange in native antenna patterns 220 may provide various means ofadapting how a communications satellite 120 provides a communicationsservice. In some examples, an adaptive beamforming system may employ thedistance between a feed array assembly 127 and the reflector 122 as acomponent of a beamforming system. For example, an arrangement ofbeamformed spot beams 125 may be determined computationally at differentcombinations of focal positions and beamforming weight matrices tooptimize the arrangement for various target parameters (e.g., coverage,average power density, system capacity, matching of spatial capacity togeographical demand). The arrangement may be determined usingcomputational techniques such as Monte Carlo analysis, iterativecomputation, and the like.

Although the change between native antenna pattern coverage area 221-d-1and native antenna pattern coverage area 221-d-2 is described as beingbased on providing different coverage area conditions for adaptingcoverage or service, a change in native antenna pattern coverage area221 may be used to respond to other circumstances. For example, a changein orbital position may modify a native antenna pattern coverage area221 for the same native antenna pattern 220, and result in a patternthat is deficient to support a communications service across the servicecoverage area 410. This condition may arise, for example, if an orbitalposition of a communications satellite 120 is at a different orbitalslot than intended, either as-deployed, as a result of satellite drift,etc. Alternatively, the change in orbital position may be a planned ordesired re-deployment of the satellite. Thus, a change in the nativeantenna pattern 220 may be dictated by circumstances external to theantenna assembly 121 or communications satellite 120, and result in achange to conditions for the service coverage area 410. The actuator 124may be used (e.g., in combination with beamforming) to return orsubstantially return the satellite operation to the desired servicecoverage area 410, for example.

FIGS. 24C and 24D illustrate native antenna pattern coverage areas 221-eand 221-f provided by native antenna patterns 220 of a communicationssatellite 120-d via multiple antenna assemblies 121, in accordance withaspects of the present disclosure. For simplicity, only the outer borderis shown for each of the native antenna pattern coverage areas 221-e and221-f, but each of the native antenna pattern coverage areas 221-e and221-f may be formed from a plurality of native feed element patterncoverage areas 211 associated with feed array assemblies 127 of a firstantenna assembly 121 and a second antenna assembly 121, as describedherein. Native antenna pattern coverage areas 221-e and 221-f may, forexample, provide one or more communications services to differentservice coverage areas 410.

FIG. 24C shows an illustration 2470 of native antenna pattern coverageareas 221-e-1 and 221-f-1 provided by the communications satellite 120-dwhile positioned in a first geostationary orbital position (e.g., anorbital slot at 98° longitude) with visible earth coverage of NorthAmerica and South America. The native antenna pattern coverage areas221-e-1 and 221-f-1 may be provided by first native antenna patterns220-e-1 and 220-f-1, which may represent first defocused conditions ofthe first and second antenna assemblies 121-g and 121-h, respectively.The communications satellite 120-d may provide a communications serviceaccording to the first native antenna pattern 220-e-1 to a first servicecoverage area 410 (not shown) that covers a substantial portion of theNorth American continent. The communications service may be provided tothe first service coverage area 410 based on the native antenna patterncoverage area 221-e-1 and other parameters (e.g., beam weights, capacitydistribution, spot beam hopping, etc.). The communications satellite120-d may provide a communications service according to the secondnative antenna pattern 220-f-1 to a second service coverage area 410(not shown) that includes a substantial portion of the South Americancontinent. The communications service may be provided to the secondservice coverage area 410 based on the native antenna pattern coveragearea 221-f-1 and other parameters (e.g., beam weights, capacitydistribution, spot beam hopping, etc.). In various examples, thecommunications services provided to the first and second servicecoverage areas 410 may be the same, or different.

FIG. 24D shows an illustration 2480 of native antenna pattern coverageareas 221-e and 221-f provided by the communications satellite 120-dwhile positioned in a second geostationary orbital position that has amore eastward position than the first geostationary orbital position.For various reasons (e.g., orbital drift, a change in deployment, etc.),the communications satellite 120-d may be moved to from the firstgeostationary orbital position to the second geostationary orbitalposition (e.g., an orbital slot at 88° longitude) for operation at thenew orbital position.

Native antenna pattern coverage areas 221-e-2 and 221-f-2 may representprojected coverage areas of the native antenna patterns 220-e-1 and 220f-1 described with reference to FIG. 24C, but at the secondgeostationary orbital position. In some examples the native antennapattern coverage areas 221-e-2 and 221-f-2 may be provided by not onlychanging the orbital position of the communications satellite 120-d, butalso by changing a boresight direction of the associated antennas 121 ofthe communications satellite 120-d (e.g., changing a skew angle asmeasured from the communications satellite 120-d between the antennaboresight direction and the center of the Earth, thereby compensatingfor the adjustment from an orbital slot at 98° to an orbital slot at88°. In some examples, this change to the antenna boresight directionmay be accomplished by causing the communications satellite 120-d to beoriented with a different attitude. However, in some examples theantennas 121 of the communications satellite 120-d may have the entireEarth in their field of view, and adjusting the boresight direction ofthe antenna assemblies may not be necessary (e.g., the antennas 121 maycontinue to be pointed at the center of the Earth.).

As shown by illustration 2480, for the same native antenna pattern220-e-1, the size of the native antenna pattern coverage area 221-e-2from the second geostationary orbital position is larger than the sizeof the native antenna pattern coverage area 221-e-1 from the firstgeostationary orbital position, due to the target area of the earthbeing rotated away from the communications satellite 120-d. In otherwords, the field of view of the first antenna assembly 121-g is broadertowards the service coverage area 410 over North America from the secondgeostationary orbital position than from the first geostationary orbitalposition, and may therefore provide a lower signal power density acrossthe desired service coverage area 410. In contrast, for the same nativeantenna pattern 220-f-1, the size of the native antenna pattern coveragearea 221-f-2 from the second geostationary orbital position is smallerthan the size of the native antenna pattern coverage area 221-f-1 fromthe first geostationary orbital position, due to the target area of theearth being rotated nearer to the communications satellite 120-d. Inother words, the field of view of the second antenna assembly 121-h isnarrower from the second geostationary orbital position than from thefirst geostationary orbital position, and may not properly cover thedesired service coverage area 410.

Although illustrated generally as a change in size, changes to a nativeantenna pattern coverage area 221 for a given native antenna pattern 220when moving from a first orbital position to a second orbital positionmay include changes in size, shape, angle of incidence of signals (e.g.,signal radiation direction) between the surface of a native antennapattern coverage area 221 and a communications satellite 120, andvarious combinations thereof. In order to continue providing acommunications service according to such changes, it may be beneficialto change a native antenna pattern 220 at an antenna assembly 121 tocompensate for such changes.

For example, in response to the change in orbital position from thefirst geostationary orbital position to the second geostationary orbitalposition, the first antenna assembly 121-g may be commanded to provide anarrower native antenna pattern 220-e-2. The change in native antennapatterns may be provided by commanding an actuator 124 of the firstantenna assembly 121-g to change from a first defocused position to asecond defocused position (e.g., by changing a length of a linearactuator). Thus, illustration 2480 shows an example of commanding anactuator of an antenna assembly 121 to provide a narrower native antennapattern 220-e-2, and the result of the narrower native antenna pattern220-e-2 may be the native antenna pattern coverage area 221-e-3.

In some examples the native antenna pattern coverage area 221-e-3 may besubstantially coextensive with the native antenna pattern coverage area221-e-1 described with reference to FIG. 24C from the firstgeostationary orbital position. Alternatively, due to changes in angleof incidence caused by the change in orbital position, the nativeantenna pattern coverage are 221-e-3 may not necessarily be coextensivewith the native antenna pattern coverage area 221-e-1, but may beotherwise provided such that the signal transmission/reception densityis similar to that provided by the native antenna pattern coverage area221-e-1, which may or may not require that the native antenna patterncoverage areas 221-e-1 and 221-e-3 be coextensive (although nativeantenna pattern coverage areas 221-e-1 and 221-e-3 may be at leastpartially overlapping). In other words, in response to a change inorbital position, the updated native antenna pattern 220-e-2 may beprovided such that a service coverage area 410 provided by the secondnative antenna pattern 220-e-2 at the second geostationary orbitalposition is substantially coextensive with the service coverage area 410provided by the first native antenna pattern 220-e-1 at the firstgeostationary position.

In another example, in response to the change in orbital position fromthe first geostationary orbital position to the second geostationaryorbital position, the second antenna assembly 121-h may be commanded toprovide a broader native antenna pattern 220-f-2. The change in nativeantenna patterns may also be provided by commanding an actuator 124 ofthe second antenna assembly 121-h to change from a first defocusedposition to a second defocused position (e.g., by changing a length of alinear actuator). Thus, illustration 2580 also shows an example ofcommanding an actuator of an antenna assembly 121 to provide a broadernative antenna pattern 220-f-2, and the result of the broader nativeantenna pattern 220-f-2 may be the native antenna pattern coverage area221-f-3.

In some examples the native antenna pattern coverage area 221-f-3 may besubstantially coextensive with the native antenna pattern coverage area221-f-1 described with reference to FIG. 24C from the firstgeostationary orbital position. Alternatively, due to changes in angleof incidence caused by the change in orbital position, the nativeantenna pattern coverage area 221-f-3 may not necessarily be coextensivewith the native antenna pattern coverage area 221-f-1 may be otherwiseprovided such that the signal transmission/reception density is similarto that provided by the native antenna pattern coverage area 221-f-1,which may or may not require that the native antenna pattern coverageareas 221-f-1 and 221-f-3 be coextensive (although native antennapattern coverage areas 221-f-1 and 221-f-3 may be at least partiallyoverlapping). In other words, in response to a change in orbitalposition, the updated native antenna pattern 220-f-2 may be providedsuch that a service coverage area 410 provided by the second nativeantenna pattern 220-f-2 at the second geostationary orbital position issubstantially coextensive with the service coverage area 410 provided bythe first native antenna pattern 220-f-1 at the first geostationaryposition.

In some cases, for a communications satellite 120 with multiple antennaassemblies 121, the native antenna pattern 220 for one antenna assembly121 may be adjusted while the native antenna pattern 220 for otherantenna assemblies 121 remain unchanged. FIG. 24E illustrates analternative for native antenna pattern coverage areas 221 provided by acommunications satellite 120-d via multiple antenna assemblies 121, inaccordance with aspects of the present disclosure. In one example, thecommunications satellite 120-d may be initially configured at the firstorbital position, as illustrated in FIG. 24C, for providing the nativeantenna pattern coverage area 221-e-1 via the first antenna assembly121-g and for providing the native antenna pattern coverage area 221-f-1via a second antenna assembly 121-h. The second antenna assembly 121-hmay be reconfigured (e.g., by commanding an actuator 124 for providing achange from the native antenna pattern 220-f-1 to the native antennapattern 220-f-3) for providing the native antenna pattern coverage area221-f-4 as shown in FIG. 24E, which may be used to provide visible earthcoverage from the first geostationary orbital position. In anotherexample, the communications satellite 120-d may be initially configuredwith the second antenna assembly 121-h adjusted to provide visible earthcoverage as illustrated in FIG. 24E (e.g., native antenna patterncoverage area 221-f-4), and subsequently the second antenna assembly121-h may be adjusted (e.g., by commanding an actuator 124) forproviding the native antenna pattern coverage area 221-f-1 as shown inFIG. 24C. Thus, illustration 2490 shows an example of commanding anactuator of one antenna assembly 121 to provide a change native antennapattern 220, while maintaining the native antenna pattern 220 of anotherantenna assembly 121.

Although described with reference to communications satellites 120having generally geostationary orbital positions, adjustments to nativeantenna patterns 220 are also applicable to non-geostationaryapplications such as LEO or MEO applications. For example, a nativeantenna pattern 220 may be adjusted to provide a larger, smaller, orotherwise adapted service coverage area that follows the orbital path ofa LEO or MEO satellite. Further, native antenna patterns 220 may beadjusted based on characteristics of the orbital path, such as theelevation and/or rate of the orbital path. This may provide designflexibility when adjustments to an orbital path are required, and/orwhen an orbital path deviates from a design orbital path. Thus, antennaassemblies 121 that support a plurality of native antenna patterns 220may also provide flexibility for beamforming of a communications serviceprovided by non-geostationary communications satellites 120.

FIGS. 25A-25C illustrate a communications satellite 120-e that supportsadjusting a relative position between a feed array assembly 127-g and areflector 122-g to support a change in native antenna patterns 220, inaccordance with aspects of the present disclosure. The communicationssatellite 120-e includes an antenna assembly 121-i having a feed arrayassembly 127-g, a reflector 122-g, and an actuator 124-g coupled betweenthe feed array assembly 127-g and the reflector 122-g.

The feed array assembly 127-g may include multiple feed elements 128-g,such as feed elements 128-g-1 and 128-g-2. Although only two antennafeed elements 128-g are shown for simplicity, a feed array assembly127-g may include any number of antenna feed elements 128-g (e.g., tens,hundreds, thousands, etc.). Moreover, the antenna feed elements 128-gmay be arranged in any suitable manner (e.g., in a linear array, anarcuate array, a planar array, a honeycomb array, a polyhedral array, aspherical array, an ellipsoidal array, or any combination thereof).

Each feed element 128 of a feed array assembly 127 may be associatedwith a gain profile, which may be examples of native feed elementpattern gain profiles 250 described with reference to FIGS. 2C and 3C.Each feed element 128 of a feed array assembly 127 may also beassociated with a respective native feed element pattern 210 (e.g.,native feed element pattern 210-g-1 associated with feed element128-g-1, native feed element pattern 210-g-2 associated with feedelement 128-g-2, etc.). Each native feed element pattern 210 may providea native feed element pattern coverage area 211 (e.g., native feedelement pattern coverage area 211-g-1 associated with native feedelement pattern 210-g-1, native feed element pattern coverage area211-g-2 associated with native feed element pattern 210-g-2, etc.),which may be examples of native feed element pattern coverage areas 211described with reference to FIGS. 2A, 2D, 3A, 3D, 4A, 24A, and 24B.Native feed element pattern coverage areas 211 may include areasprojected on a reference plane 2505, and/or volume above or below thereference plane 2505, after reflection from the reflector, as describedherein.

The reflector 122-g may be configured to reflect signals transmittedbetween the feed array assembly and one or more target devices (e.g.,access node terminals 130 and/or user terminals 150). The reflectorsurface may be of any suitable shape for distributing signals betweenthe feed array assembly 127-g and a service coverage area 410 of thecommunications satellite 120-e, which may include a parabolic shape, aspherical shape, a polygonal shape, etc. Although only a singlereflector 122-g is illustrated, a communications satellite 120 mayinclude more than one reflector 122 for a particular feed array assembly127. Moreover, a reflector 122 of a communications satellite 120 may bededicated to a single feed array assembly 127, or shared betweenmultiple feed array assemblies 127.

The reflector 122-g may be associated with a focal region 123, which mayrefer to one or more locations at which signals received by thecommunications satellite 120 a are concentrated, as described withreference to FIGS. 2A and 2B. For example, a focal region of reflector122-g may refer to a location at which those signals that arrive at thereflector in a direction parallel to a primary axis of the reflector122-g are reflected to a coincident point. Conversely, the focal regionof the reflector 122-g may refer to the location from which signals thatare emitted from the focal region reflect off the reflector in a planewave.

In some examples it may be advantageous to position the feed arrayassembly 127-g at a defocused position with respect to the reflector122-g (e.g., between the surface of the reflector 122-g and the focalregion of the reflector 122-g, or some other defocused position withrespect to the reflector 122-g). As used herein, feed array assembly127-g being located at a defocused position with respect to thereflector 122-g may refer to a feed element 128-g (e.g., an opening of afeed aperture, a transducer of a feed, etc.) being located at a distancefrom a reflector that is different than a distance between the reflector122-g and the focal region of the reflector 122-g. In some examples feedarray assembly 127-g being located at a defocused position with respectto the reflector 122-g may refer to a surface of antenna feed elements128-g (e.g., a reference surface of a plurality of feed apertureopenings, a reference surface of a plurality of feed transducers, etc.)being located at a distance from a reflector 122-g along a referenceaxis that is different from the distance between the reflector 122-g anda focal region along the reference axis. Such an arrangement may resultin broader native feed element pattern coverage areas 211 than when thefeed array assembly 127-g is positioned at the focal region of thereflector 122-g, which may improve flexibility for beamforming of spotbeams 125. For example, with broader native feed element patterncoverage areas 211, a greater quantity of antenna feed elements 128-g ofa feed array assembly 127-g may be able to support a particular spotbeam coverage area 126. Moreover, broader native feed element patterns210-g may also allow each feed element 128-g of the feed array assembly127-g to support a greater quantity of spot beam coverage areas 126.

The actuator 124-g may support adjusting a relative distance between thefeed array assembly 127-g and the reflector 122-g. For example, theactuator 124-a may be a linear actuator that is constrained to providethe change in relative distance along one translational direction, whichmay be aligned along a direction predominantly between a center of thereflector 122-g and a focal region of the reflector 122-g. In variousexamples the actuator 124-g may include a linear motor, a stepper motor,a servo motor, a rack and pinion assembly, a ball screw assembly, akinematic linkage, an extendable truss assembly, a hydraulic cylinder,or any combination thereof.

As illustrated in FIGS. 25A-25C, the feed array assembly 127-g may befixed with respect to the body of the communications satellite 120-g,and therefore the actuator 124-g may move the reflector 122-g along anaxis with respect to the body of the communications satellite 120-e. Inother examples, the reflector 122-g may be fixed with respect to thebody of the communications satellite 120-e, and therefore the linearactuator 124-g may move the feed array assembly 127-g along an axis withrespect to the body of the communications satellite 120-e. In yet otherexamples, neither the feed array assembly 127-g nor the reflector 122-gmay be fixed with respect to the body of the communications satellite120-e, and the actuator 124-g may move one or both of the feed arrayassembly 127-g or reflector 122-g along an axis with respect to the bodyof the communications satellite 120-e (e.g., in a combined manner, in acoordinated manner, in a separate manner, etc.).

In some examples the communications satellite 120-e may includeadditional actuators, such as a secondary actuators 2540 a and/or2540-b. Secondary actuators 2540 may be configured to provide one ormore additional degrees of freedom (e.g., a rotational degree offreedom, a translational degree of freedom, or a combination thereof)between the feed array assembly 127-g and the reflector 122-g. In suchexamples, a secondary actuator 2540 may be commanded to cause a changein relative position between the feed array assembly and the reflectorabout an axis different from an axis of the actuator 124-g, with such achange combining with the adjustment of the actuator 124-g to providethe commanded change in native antenna patterns. Secondary actuators2540 may include one or more suitable components for providing suchadditional degrees of freedom between the feed array assembly 127-g andthe reflector 122-g. For example, a secondary actuator 2540 may includea hinge or ball joint that may be actuated to compensate for satellitewobble (e.g., rotational vibration that may affect antenna boresightdirection). Although secondary actuator 2540 a is illustrated asproviding a rotational coupling between a body portion of thecommunications satellite 120-e and the actuator 124-g, and secondaryactuator 2540-g is illustrated as providing a rotational couplingbetween the actuator 124-g and the reflector 122-g, additional actuatorsmay be coupled in any suitable location with any suitable degree(s) offreedom between the feed array assembly 127-g and the reflector 122-g.

FIG. 25A illustrates an example 2500 of the communications satellite120-e having a first distance (e.g., distance d₁) between the feed arrayassembly 127-g and the reflector 122-g corresponding to a focusedarrangement of the antenna assembly 121-g. In the arrangement of example2500, the native feed element patterns 210-g may be relatively narrow(e.g., as shown by native feed element patterns 210-g-1 and 210-g-2).Accordingly, the native feed element pattern coverage areas 211-g withrespect to reference plane 2505 may be relatively small (e.g., as shownby native feed element pattern coverage areas 211-g-1 and 211-g-2), andthe resulting native antenna pattern 220 may be referred to as having alow native feed element pattern overlap condition.

In some examples, a low native feed element pattern overlap condition isassociated with each feed element 128 having less than half of itsnative feed element pattern 210 overlapping with a native feed elementpattern 210 of any given neighboring feed element 128. In otherexamples, a low native feed element pattern overlap condition may bedescribed as each feed element 128 having less than 40 percent, 30percent, 20 percent, or 10 percent of its native feed element pattern210 overlapping with a native feed element pattern 210 of any givenneighboring feed element 128. In yet other examples, a low native feedelement pattern overlap condition may be described as each feed element128 having no overlap of its native feed element pattern 210 with anative feed element pattern 210 of any given neighboring feed element128.

In various examples, distance d₁ may cause the distance between the feedarray assembly 127-g and the reflector 122-g to be equal to, orrelatively near a focal distance of the reflector 122-g (e.g., a zerofocal offset distance). While example 2500 may represent the feed arrayassembly 127-g being at a lightly defocused position with respect to thereflector 122-g because neighboring native feed element pattern coverageareas 211-g have some beam overlap with each other, example 2500 isconsidered to be a focused position of antenna assembly 121-i for thepurposes of this description. In other words, a low beam overlapcondition of native feed element pattern coverage areas 211 isconsidered for the purposes of this description to be a result of afocused position of an antenna assembly 121.

FIG. 25B illustrates an example 2550 of the communications satellite120-e having the antenna assembly 121-g in a first defocused position.In example, 2550, the actuator 124-g provides a relatively smalldistance (e.g., distance d₂), resulting in the feed array assembly 127-gbeing nearer to the reflector 122-g than the focal region of thereflector 122-g (e.g., the feed array assembly 127-g may be closer tothe reflector 122-g than in example 2500). In other words, example 2550may represent the feed array assembly 127-g being located at a heavilydefocused position with respect to the reflector 122-g. In thearrangement of example 2550, the native feed element patterns 210-h maybe relatively wide (e.g., as shown by native feed element patterns210-h-1 and 210-h-2). Accordingly, the native feed element patterncoverage areas 211-h with respect to reference plane 2505 may berelatively large (e.g., as shown by native feed element pattern coverageareas 211-h-1 and 211-h-2).

FIG. 25C illustrates an example 2555 of the communications satellite120-e having the antenna assembly 121-i in a second defocused position.In example 2555, the actuator 124-g has been adjusted to increase thedistance between the feed array assembly 127-g and the reflector 122-gfrom distance d₂ to distance d₃. In the arrangement of example 2555, thenative feed element patterns 210-i may be relatively wide and havesubstantial overlap (e.g., as shown by native feed element patterncoverage areas 211-i-1 and 211-i-2), but may each be narrower than inthe arrangement of example 2550.

Example 2550 may represent a first operating condition (e.g., a firstnative antenna pattern 220-h) of the communications satellite 120-e thatsupports a communications service according to a first native antennapattern, wherein the first native antenna pattern 220-h is based atleast in part on the length of, or the length otherwise provided by theactuator 124-g (e.g., distance d₂). The first native antenna pattern220-h may be characterized by such features as the size of the nativefeed element pattern coverage areas 211-h, a degree of overlap betweennative feed element pattern coverage areas 211-h, locations of nativefeed element pattern coverage areas 211-h, or other characteristics ofthe native feed element pattern coverage areas 211-h. Although only twonative feed element pattern coverage areas 211-h are shown in example2550, a communications satellite 120 may have any number (e.g., tens,hundreds, thousands, etc.) of native feed element pattern coverage areas211.

Example 2555 may represent a second condition (e.g., a second nativeantenna pattern 220-i) of the communications satellite 120-e thatsupports a communications service according to a second native antennapattern 220-i, wherein the second coverage condition is based at leastin part on the length of, or the length otherwise provide by theactuator 124-g (e.g., distance d₃). As the beamwidth of each native feedelement pattern 210-i is different than native feed element patterns210-h of the first condition, the features of the second native antennapattern 220-i may be different from the first condition. Such changes infeatures between the first native antenna pattern 220-h and the secondnative antenna pattern 220-i may support, for example, variousbeamforming operations according to different defocused conditions, asdescribed herein.

The actuator 124-g may be configured for distances between the feedarray and the reflector that are not illustrated in FIGS. 25A, 25B, or25C, such as distances greater than d₁, less than d₂, or in-between d₁,and d₂. Thus, as described herein, the actuator 124-g may provide achange in relative distance between the feed array assembly 127-g andthe reflector 122-g, and accordingly provide a change in the nativeantenna pattern 220 which may be used to provide service according to avariety of native antenna patterns 220. For example, changing the lengthof the actuator 124-g may be used to change the beam width and amount ofoverlap of native feed element patterns in the antenna pattern. Changingthe length of the actuator 124-g may also be used to distribute energyreceived from a given location (e.g., a location in a service coveragearea 410) to more feed elements 128 of a feed array assembly 127.

Although the adjustment shown between example 2550 and example 2555 isillustrated to show a change in size, degree of overlap, and location ofnative feed element pattern coverage areas 211, in some examples othercharacteristics may be changed to provide different conditions. Forexample, secondary actuator assemblies 440 may be used to changepointing direction of a native antenna pattern 220. Thus, an antennaassembly 121 may be configured such that the adjustment of an actuator124 coupled between a feed array assembly 127 and a reflector 122 mayprovide various desired changes in characteristics and/or ratios orrelationships of multiple characteristics between native feed elementpattern coverage areas 211.

FIG. 25D illustrates an example diagram 2575 of a communicationssatellite 120-f that supports adjusting a relative position between feedarray assemblies 127 and reflectors 122 to support a change in nativeantenna patterns for two antenna assemblies 121, in accordance withaspects of the present disclosure. For example, communications satellite120-f includes antenna assemblies 121-j and 121-k for supportingmultiple independent native antenna pattern coverage areas (e.g., nativeantenna pattern coverage areas 221-j and 221-k). For example, a firstantenna assembly 121-j may provide a communication service to a firstnative antenna pattern coverage area 221-j while a second antennaassembly 121-k may provide a communication service to a second nativeantenna pattern coverage area 221-k. In the illustrated example, thefirst antenna assembly 121-j includes a first actuator 124-j (e.g., alinear actuator coupled between the feed array assembly 127-j and thereflector 122-j) that adjusts a relative distance between a first feedarray assembly 127-j and a first reflector 122-j to provide the firstnative antenna pattern coverage area 221-j. The second antenna assembly121-k includes a second actuator 124-k (e.g., a linear actuator coupledbetween the second feed array assembly 127-k and the second reflector122-k) that adjusts a relative distance between the second feed arrayassembly 127-k and the second reflector 122-k to provide a second nativeantenna pattern coverage area 221-k. The first and second native antennapatterns 221-j and 221-k may each be a composite of multiple native feedelement pattern coverage areas 211 (only two of which are shown for eachnative antenna pattern coverage area 221 for clarity). Thus, eachantenna assembly 121 may have an independently controlled native antennapattern 220 via separate actuators 124.

In some examples, the first antenna assembly 121-j is associated with auser terminal service coverage area 410 and the second antenna assembly121-k is associated with an access node terminal service coverage area410. For instance, communication signals between user terminals 150 andthe communications satellite 120-f may be communicated according to thefirst native antenna pattern coverage area 221-j, which is dependent ona first native antenna pattern 220-j provided by the first antennaassembly 121-j while communication signals between access node terminals130 and the communications satellite 120-f may be communicated accordingto a second native antenna pattern coverage area 221-k that is dependenton a second native antenna pattern 220-k provided by the second antennaassembly 121-k. Thus, different service coverage areas 410 may beprovided a communications service according to different native antennapatterns 220 via separate antenna assemblies 121. Although illustratedwith two antenna assemblies 121, a communications satellite 120 may havemore than two antenna assemblies 121, including multiple antennaassemblies 121 associated with corresponding access node terminalservice coverage areas 410 and/or multiple antenna assemblies 121associated with corresponding user terminal service coverage areas 410.

FIGS. 26A & 26B illustrate an example of a communications satellite120-g having an antenna assembly 121-l with a reflector-based actuator124-l that may support changes in native antenna pattern coverage areas221-l, in accordance with aspects of the present disclosure. Theactuator 124-l may cause the reflector 122-l to change shape, such thatthe location of the focal region 123 of the reflector 122-l changeslocation. For example, in condition 2605 of FIG. 26A, the focal region123 of the reflector 122-l may be relatively far from the reflector122-l. Accordingly, the native antenna pattern 220-l-1 may be relativelybroad, such that the native antenna pattern coverage area 221-l-1projected on the reference plane 2505-l is consequently relatively wide.By contrast, in condition 2610 of FIG. 26B, the focal region 123 of thereflector 122-l may be relatively near to the reflector 122-l.Accordingly, the native antenna pattern 220-l-2 may be relativelynarrow, such that the native antenna pattern coverage area 221-l-2projected on the reference plane 2505-l is consequently relativelynarrow.

Various mechanisms, or combinations of mechanisms may provide thefunction of the reflector-based actuator 124-l, such as a collection oflinear actuators, a cable and pulley system, a kinematic linkage, or anyother mechanism that changes the shape of a reflector 122, and therebychanges the characteristics of a focal region 123 of the reflector 122.Such changes to a focal region 123 of a reflector 122 may include movingfrom a first focal point to a different focal point, changing from asingle focal point to a plurality of focal points, changing from a focalpoint to a focal line or focal surface, changing from a focal line to afocal point or a focal surface, changing from a focal surface having afirst shape to a focal surface having a second shape, or variouscombinations thereof. Furthermore, a reflector 122 may include anactuator 124 that changes the shape of all of, or a portion of thereflector 122, and in some examples a reflector may have more than oneactuator 124 to change various portions of the reflector shape. Thus,various types of reflector-based actuators 124 may be used to adjust anative antenna pattern 220 of an antenna assembly 121.

FIGS. 26C & 26D illustrate an example of a communications satellite120-h having an antenna assembly 121-m with an actuator 124-m integratedwith a feed array assembly that may support changes in native antennapattern coverage areas 221-m, in accordance with aspects of the presentdisclosure. Antenna assembly 121-m does not include a reflector, andinstead illustrates an example of a direct radiating array (DRA) antennaassembly 121. For the antenna assembly 121-m, the actuator 124-m maycause the arrangement of antenna feed elements 128-m of the feed arrayassembly 127-m to change characteristics, such that the native feedelement patterns 210 associated with the feed elements 128 are pointedto a different location. Accordingly, the actuator 124-m may change theshape, orientation, and/or distribution of native feed element patterns210, thereby changing the native antenna pattern coverage area 221-m forthe antenna assembly 121-m. For example, in condition 2615 of FIG. 26C,the actuator 124-m may be commanded to provide a relatively narrowdistribution of native feed element patterns 210-m (e.g., a tightdistribution of pointing directions for each of the feed elements128-m), such that the native antenna pattern coverage area 221-m-1projected on the reference plane 2505-m is consequently relativelynarrow. By contrast, in condition 2620 of FIG. 26D, the actuator 124-mmay be commanded to provide a relatively wide distribution of nativefeed element patterns 210-m (e.g., a wide distribution of pointingdirections for each of the feed elements 128-m), such that the nativeantenna pattern coverage area 221-m-1 projected on the reference plane2505-m is consequently relatively broad.

Various mechanisms, or combinations of mechanisms may provide thefunction of the actuator 124-m that is integrated into the feed arrayassembly 127-m. For example, a mechanism may be provided to change theshape of the feed array assembly 127-m, such as a mechanism to changethe curvature of a surface of the feed array assembly 127-m thatincludes the feed horn apertures of the feed elements 128-m. In otherexamples, one or more actuators 124-m may be provided to change theorientation of the feed elements 128-m, without changing the shape ofthe feed array assembly 127-m. Furthermore, a feed array assembly 127may include an actuator 124 that changes the orientation and/or nativefeed element pattern 210 of all of, or a portion of the feed elements128 of the feed array assembly 127, and in some examples a feed arrayassembly 127 may have more than one actuator 124 to change variousportions of the feed array assembly 127. Thus, various types ofactuators 124 may be integrated into a feed array assembly to adjust anative antenna pattern 220 of an antenna assembly 121.

FIGS. 26E & 26F illustrate an example of a communications satellite120-i having an antenna assembly 121-n with an actuator 124-n coupledbetween a first reflector 122-n-1 and a second reflector 122-n-2, andmay support changes in native antenna pattern coverage areas 221-n, inaccordance with aspects of the present disclosure. The actuator 124-nmay cause the second reflector 122-n-2 to be nearer or farther from thefirst reflector 122-n-1. For example, in condition 2625 of FIG. 26E, thesecond reflector 122-n-2 may be relatively far near to the firstreflector 122-n-1. Accordingly, the native antenna pattern 220-n-1 maybe relatively broad, such that the native antenna pattern coverage area221-n-1 projected on the reference plane 2505-n is consequentlyrelatively wide. By contrast, in condition 2620 of FIG. 26E, the secondreflector 122-n-2 may be relatively far from the first reflector122-n-1. Accordingly, the native antenna pattern 220-n-2 may berelatively narrow, such that the native antenna pattern coverage area221-n-2 projected on the reference plane 2505-n is consequentlyrelatively narrow. Various mechanisms, or combinations of mechanisms mayprovide the function of the actuator 124-n that is coupled between afirst reflector 122 and a second reflector 122, including any of theactuators 124 described with reference to an actuator 124 coupledbetween a reflector 122 and a feed array assembly 127.

FIG. 27 illustrates a block diagram 2700 of a communications satellite120-j that supports providing a communications service according to aplurality of native antenna patterns 220, in accordance with aspects ofthe present disclosure. The communications satellite 120-j may be anexample of one or more of the communications satellites 120 describedherein, and may include a feed array assembly 127-o, a reflector 122-o,an actuator 124-o, an actuator controller 2720, and a satellitecommunications manager 2730.

The feed array assembly 127-o may be an example of any of the feed arrayassemblies 127 described herein, and may include a plurality of antennafeed elements 128 arranged in any suitable manner to support a pluralityof native feed element patterns 210. The reflector 122-o may be anexample of any of the reflectors 122 described herein, and may beconfigured to reflect signals transmitted between the feed arrayassembly 127-o and one or more target devices (e.g., access nodeterminals 130 and/or user terminals 150). Although only feed arrayassembly 127-o and one reflector 122-o are illustrated, a communicationssatellite 120 such as communications satellite 120-j may include morethan one feed array assembly 127 and/or more than one reflector 122.

Actuator 124-o may be an example of any of the actuators 124 describedherein for supporting a communications service according to a pluralityof native antenna patterns 220. For example, actuator 124-o may be alinear actuator coupled between the reflector 122-o and the feed arrayassembly 127-o, and may support adjusting a relative distance betweenthe feed array assembly 127-o and the reflector 122-o. The actuator124-o may be constrained to provide the change in relative distancealong one translational direction, which may be aligned along adirection predominantly between a center of the reflector 122-o and afocal region 123 of the reflector 122-o. In various examples theactuator 124-o may include linear motor, a stepper motor, a servo motor,a rack and pinion assembly, a ball screw assembly, a kinematic linkage,an extendable truss assembly, a hydraulic cylinder, or any combinationthereof. In other examples the actuator 124-o may be coupled between tworeflectors 122, integrated in a feed array assembly 127, orreflector-based, as described with reference to FIGS. 26A through 26F.In some examples the communications satellite 120-j may optionallyinclude additional actuators, such as secondary actuator 2540-c, whichmay be an example of secondary actuator 2540 described with reference toFIGS. 25A-25C, or an orbital position actuator 2740 (e.g., a thruster, aflywheel, etc.) for adjusting an orientation (e.g., attitude) orlocation of the communications satellite 120-j.

The actuator controller 2720 may be configured to define, command,and/or monitor various states of one or more actuators (e.g., theactuator 124-o, the secondary actuator 2540-o, the orbital positionactuator 2740, etc.) of the communications satellite 120-j, and mayprovide other high-level functions of actuation control. States of theactuator controller 2720 can include initialization states, operationalstates, and/or fault states, and the actuator controller can changebetween states or maintain a particular state in response topre-programmed commands and/or signals received from the one or moreactuators, the satellite communications manager, and/or signals fromoutside the actuator controller 2720 such as position detectors and/orencoders, sensors, relays, user commands, or any other control signal.The actuator controller 2720 may generate various control signals thatare delivered to the one or more actuators in response to pre-programmedinstructions (e.g., operational configurations, control algorithms,controller gains, offsets, deadbands, multipliers, etc.) and/or receivedsignals. For example, the actuator controller 2720 may include anactuator driver 2721, which may support actuation of the actuator 124-oaccording to command signals of the actuator controller 2720. Incommunications satellites 120 that include a secondary actuator and/oran orbital position actuator, an actuator controller 2720 may optionallyinclude a secondary actuator driver 2724 and/or an orbital positionactuator driver 2725, respectively.

In various examples, the command signals described herein may bereceived by the actuator controller 2720 and/or determined by theactuator controller 2720. For example, the actuator controller mayoptionally include a command signal receiver 2722, which may supportreceiving (e.g., via the satellite communications manager 2730) acommand signal for controlling the actuator 124-o (and/or otheractuators, when present) from a command signal generator, such as aterrestrial access node terminal 130 or other network device 141configured to control aspects of providing a communications serviceaccording to various native antenna patterns 220. Additionally oralternatively, the actuator controller 2720 may include a command signaldeterminer 2723 that supports determining (e.g., at the communicationssatellite 120-j) a command signal for actuating the actuator 124-o(and/or other actuators, when present) to provide a desired nativeantenna pattern 220. In various examples, command signals may includeindications of actuator positions, a difference between positions, adesired position of a component of the communications satellite 120-j(e.g., the reflector 122-o, the feed array assembly 127-o, etc.), alength or angle of an actuator, a parameter of a native antenna pattern220, a lookup value associated with the second native antenna pattern220, or any other command signal suitable for identifying or determininghow to drive a particular actuator 124 and/or secondary actuator 2540 toachieve a desired result.

The satellite communications manager 2730 may be configured to manageone or more aspects of providing a communications service via thecommunications satellite 120-j. For example, the satellitecommunications manager 2730 may manage communication via signals 2705provided to, or received from (e.g., via transceiver(s) 2710) otherdevices, such as access node terminals 130, network devices 141, userterminals 150, CPEs 160, etc. In some examples, signals 2705 may be partof the communications service provided via the communications satellite120-j. Additionally or alternatively, signals 2705 may include controlsignals or diagnostic or control information unrelated to thecommunications service, but otherwise provided by, or received by thecommunications satellite 120-j.

Some examples of a satellite communications manager 2730 may optionallyinclude a coverage area manager 2731, which may manage one or moreaspects of coverage areas as described herein. For example, the coveragearea manager 2731 may include a database, equations, or otherconfiguration that supports providing, monitoring, and/or adjustingnative antenna patterns 220 for providing a communications service viathe communications satellite 120-o. The coverage area manager 2731 may,for example, include algorithms for determining and/or providing adesired native antenna pattern 220, native feed element pattern coveragearea 211, native feed element pattern coverage area overlap, and thelike. In some examples the coverage area manager 2731 may be operablebased at least in part on characteristics of the actuator 124-o, aposition or rotation of the secondary actuator 2540-o, an orbitalposition, or a change in orbital position (e.g., to calculate coveragearea parameters, to trigger a change in a native antenna pattern 220,etc.). In other examples, coverage area management may be performed bysome other device, such as a communications service manager as describedherein.

In examples where the satellite communications manager 2730 provides acommunications service by way of beamforming, the satellitecommunications manager may optionally include a beamforming manager2732. The beamforming manager 2732 may, for example, support on-boardbeamforming at the communications satellite 120-j, and may include a BFN710 and/or a BWP 714 as described herein. For example, the beamformingmanager 2732 may apply a beamforming weight set to signals 2705 carriedvia the feed array assembly 127-o. Beam weights of the beamformingweight set may, for example, be applied to signals prior to transmissionto support directional transmission of Tx spot beams 125, or may beapplied to signals received by the communications satellite 120-o tosupport directional reception of Rx spot beams 125. In various examples,such beam weights may be selected and/or calculated by the beamformingmanager (e.g., at a BWP 714) in order to provide a desired nativeantenna pattern 220 (e.g., to provide a desired size and/or position ofspot beam coverage areas 126, to provide a desired degree of overlapamongst a plurality of spot beam coverage areas 126, to assign a desiredset of antenna feed elements 128 of the feed array assembly 128-o usedfor one or more spot beams 125, etc.). In other examples, beamformingmanagement may be performed by some other device, such as acommunications service manager as described herein.

The actuator controller 2720 and/or the satellite communications manager2730 may be implemented or performed, individually or collectively, witha general-purpose processor, a digital signal processor (DSP), an ASIC,an FPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

FIG. 28 shows a block diagram 2800 of a satellite controller 2805 thatsupports providing a communications service according to a plurality ofnative antenna patterns, in accordance with aspects of the presentdisclosure. The satellite controller 2805 may include a processor 2810,memory 2815, an actuator controller 2720 a, a satellite communicationsmanager 2730 a, and a communications interface 2840. Each of thesecomponents may be in communication with each other, directly orindirectly, over one or more buses 2835.

The memory 2815 may include random access memory (RAM) and/or read-onlymemory (ROM). The memory 2815 may store an operating system (OS) 2820(e.g., built on a Linux or Windows kernel). The memory 2815 may alsostore computer-readable, computer-executable code 2825 includinginstructions that are configured to, when executed, cause the processor2810 to perform various functions described herein related providing acommunications service according to different native antenna patterns.Alternatively, the code 2825 may not be directly executable by theprocessor 2810 but be configured to cause the satellite controller 2805(e.g., when compiled and executed) to perform one or more of thefunctions described herein.

The satellite controller may include an actuator controller 2720 a,which may be an example of the actuator controller 2720 of FIG. 27. Theactuator controller 2720 a may control a linear actuator to provide achange in relative distance between a feed array assembly and areflector, as described herein. The satellite communications manager2730-a may support providing a communications service according to anative antenna pattern, as described herein. In some examples operationsmay be supported by the communications interface 2840, which may providefor signals 2845 to be transmitted to, or received from other featuresof a communications satellite (e.g., a feed array assembly, one or moreactuators, etc.) By supporting the features described herein, acommunications satellite 120 that includes the satellite controller 2805may therefore support providing a communications service according todifferent native antenna patterns.

The satellite controller 2805, including the processor 2810, the memory2815, the actuator controller 2720 a, and satellite communicationsmanager 2730 a, and/or the communications interface 2840 may beimplemented or performed with a general-purpose processor, a digitalsignal processor (DSP), an ASIC, an FPGA or other programmable logicdevice, discrete gate or transistor logic, discrete hardware components,or any combination thereof designed to perform the functions describedherein. A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. The satellite controller2805 may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, integrated memory, discrete memory, or any other suchconfiguration.

FIG. 29 shows a block diagram 2900 of a communications service manager2905 that supports providing a communications service according to aplurality of native antenna patterns, in accordance with aspects of thepresent disclosure. The communications service manager 2905 may includea communications manager 2910 and a command signal determiner 2920.

The communications manager 2910 may manage aspects of communicationsthat are provide by the communications service, such as forward linkcommunications and return link communications. For example, thecommunications manager 2910 may manage one or more aspects of theproviding of a first plurality of signals between a plurality of accessnode terminals and a satellite, and the providing a second plurality ofsignals between the satellite and a plurality of terminals.

The command signal determiner 2920 may determine one or more commandsignals to be provided to a communications satellite to adapt how acommunications service is provided. For example, the command signaldeterminer 2920 may determine a command for a linear actuator of acommunications satellite to change from the first length to a secondlength, which may provide a change in a relative distance between a feedarray assembly and a reflector of the communications satellite. Thechange in length of the linear actuator of the communications satellitemay subsequently support providing a communications service according toa new native antenna pattern.

The coverage area manager 2930 may manage various parameters and/orequations relating to coverage areas of the communications satellite. Insome examples the coverage area manager may determine aspects of thecoverage areas based at least in part on a length of a linear actuatorof the communications satellite, a position or rotation of a secondactuator, an orbital position of the communications satellite, or anycombination thereof which may be detected by the communications servicemanager 2905, or received from the communications satellite itself. Thecoverage area manager 2930 may be used to identify a desired nativeantenna pattern and/or determine a change in native antenna patterns totrigger the command signal determiner 2920 to initiate a command to anactuator of the communications satellite.

In examples where the communications service manager 2905 manages acommunications service that employs beamforming, the communicationsservice manager may optionally include a beamforming manager 2940. Thebeamforming manager 2940 may, for example, support ground-basedbeamforming via a communications satellite 120. For example, thebeamforming manager 2940 may apply a set of beamforming coefficients tosignals transmitted by an access node terminal 130. Such beamformingcoefficients may, for example, be applied to signals prior totransmission to support directional transmission, or may be applied tosignals received by the communications satellite 120 to supportdirectional reception. In other examples, such beamforming coefficientsmay be determined by the beamforming manager 940, and provided to acommunications satellite 120 in order to support on-board beamforming atthe communications satellite. In various examples, beamformingcoefficients may be selected and/or calculated by the beamformingmanager 2940 in order to provide a desired native antenna patterndetermined by the communications service manager 2905.

FIG. 30 shows a block diagram 3000 of a communications servicecontroller 3005 that supports providing a communications serviceaccording to a plurality of native antenna patterns, in accordance withaspects of the present disclosure. The communications service controller3005 may include a processor 3010, memory 3015, a communications servicemanager 2905-a, and a communications interface 3040. Each of thesecomponents may be in communication with each other, directly orindirectly, over one or more buses 3035. In various examples, thecommunications service controller 3005 may be, or be part of an accessnode terminal 130 or a network device 141 described with reference toFIG. 1A.

The memory 3015 may include random access memory (RAM) and/or read-onlymemory (ROM). The memory 3015 may store an operating system (OS) 3020(e.g., built on a Linux or Windows kernel). The memory 3015 may alsostore computer-readable, computer-executable code 3025 includinginstructions that are configured to, when executed, cause the processor3010 to perform various functions described herein related providing acommunications service according to different native antenna patterns.Alternatively, the code 3025 may not be directly executable by theprocessor 3010 but be configured to cause the communications servicecontroller 3005 (e.g., when compiled and executed) to perform one ormore of the functions described herein.

The satellite controller may include a communications service manager2905-a, which may be an example of the communications service manager2905 of FIG. 29. The communications service manager 2905-a may manageone or more aspects of providing a communications service according todifferent native antenna patterns, as described herein. Thecommunications service may, for example, be provided via thecommunications interface 3040. In some examples the communicationsservice manager may determine a desired native antenna pattern, andsubsequently determine a command to be sent to a communicationssatellite 120 (e.g., by way of signaling 3045 via the communicationsinterface 3040) to provide the desired native antenna pattern. Forexample, the determined command may indicate a change in a positionand/or length of a linear actuator to provide a change in relativedistance between a feed array assembly and a reflector, whichsubsequently provides the change in native antenna pattern.

The communications service controller 3005, including the processor3010, the memory 3015, the communications service manager 2905-a, and/orthe communications interface 3040 may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. The communications service controller 3005 may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, integrated memory,discrete memory, or any other such configuration

FIG. 31 illustrates a flow chart of an example method 3100 that supportsproviding a communications service via a communications satelliteaccording to a plurality of native antenna patterns, in accordance withaspects of the present disclosure. The method 3100 is described belowwith reference to one or more aspects of a communications satellite 120having a feed array assembly 127, a reflector 122, and a linear actuator124 coupled between the feed array assembly, as described herein. Insome examples, the communications satellite 120 itself may perform oneor more of the operations of method 3100 described below. In someexamples, one or more of the operations of method 3100 may be performedby a communications service controller 3005.

At 3105, the method 3100 may include providing a communications servicevia the satellite according to a first native antenna pattern of asatellite antenna of the satellite, as described herein. The firstnative antenna pattern may include a first plurality of spot beams, andmay be based at least in part on a first length of the linear actuatorproviding a first defocused position of a feed array assembly relativeto a reflector of the satellite antenna. Providing the communicationsservice may include providing a first plurality of signals between aplurality of access node terminals and the satellite and providing asecond plurality of signals between the satellite and a plurality ofterminals. In some examples the first defocused position may beassociate with the feed array assembly being located between thereflector and a focal region of the reflector. The communicationsservice may be provided by way of beamforming, and providing thecommunications service according to the first native antenna pattern mayinclude applying a first set of beamforming coefficients to signalscarried via the feed array assembly. The described beamformingcoefficients may be determined at the communications satellite 120, ormay be determined at another device such as a communications servicecontroller 3005, and subsequently provided to the communicationssatellite 120 (e.g., by way of wireless transmissions received at thecommunications satellite 120).

At 3110, the method 3100 may include commanding the linear actuator tochange from the first length to a second length, as described herein. Invarious examples, the commanding at 3110 may include providing anindication of a new position of the linear actuator, a differencebetween position, a desired position of the reflector, a desiredposition of the feed array assembly, a length of the linear actuator, aparameter of the second native antenna pattern, or a lookup valueassociated with the second native antenna pattern. The commanding at3110 may be determined at the communications satellite 120, or may bedetermined at another device such as a communications service controller3005, and subsequently provided to the communications satellite 120(e.g., by way of wireless transmissions received at the communicationssatellite 120).

In some examples, at 3115 the method 3100 may optionally includecommanding a second actuator. The second actuator may be coupled betweenthe feed array assembly and the reflector, and may support causing achange in relative position between the feed array assembly and thereflector about an axis different from an axis along the first and thesecond lengths of the linear actuator. The commanding at 3115 may bedetermined at the communications satellite 120, or may be determined atanother device such as a communications service controller 3005, andsubsequently provided to the communications satellite 120 (e.g., by wayof wireless transmissions received at the communications satellite 120).

In some examples, at 3120 the method 3100 may optionally includecommanding the satellite to move from the first orbital position to asecond orbital position. The commanding at 3120 may be determined at thecommunications satellite 120, or may be determined at another devicesuch as a communications service controller 3005, and subsequentlyprovided to the communications satellite 120 (e.g., by way of wirelesstransmissions received at the communications satellite 120).

At 3125, the method 3100 may include providing the communicationsservice via the satellite according to a second native antenna patternof the satellite antenna. The second native antenna pattern may includea second plurality of spot beams, and may be based at least in part onthe second length of the linear actuator providing a second defocusedposition of the feed array assembly relative to the reflector. Thesecond defocused position may provide various differences of the secondnative antenna pattern when compared to the first native antennapattern. For example, the second defocused position may provide a secondnative feed element pattern coverage area size of the feed of the feedarray assembly that is different from the first native feed elementpattern coverage area size. In some examples the second defocusedposition provides a second overlap of native feed element patterns ofthe two or more antenna feed elements of the feed array assembly that isdifferent from the first overlap of native feed element patterns.

In some examples, the communications service at 3125 may be provided viathe communications satellite at the same orbital position as thecommunications service provided at 3105, and the second native antennapattern may correspond to a different service coverage area than thefirst native antenna pattern. In some examples the service coverage areaof the second native antenna pattern may at least partially overlap theservice coverage area of the first native antenna pattern. Providing thecommunications service at 3125 may include applying a different set ofbeamforming coefficients to signals carried via the feed array assembly.The described beamforming coefficients may be determined at thecommunications satellite 120, or may be determined at another devicesuch as a communications service controller 3005 and subsequentlyprovided to the communications satellite 120 (e.g., by way of wirelesstransmissions received at the communications satellite 120).

Thus, method 3100 may support providing a communications serviceaccording to different native antenna patterns, wherein the differentnative antenna patterns are based at least in part on the commanding ofa linear actuator coupled between a feed array assembly and a reflectorof a communications satellite. It should be noted that method 3100discusses exemplary implementations and that the operations of method3100 may be rearranged or otherwise modified such that otherimplementations are possible. For example, certain described operationsmay be optional (e.g., those enclosed by boxes having dashed lines,those described as optional, etc.), wherein optional operations may beperformed when certain criteria are met, performed based on aconfiguration, omitted intermittently, omitted entirely, etc.

The detailed description set forth above in connection with the appendeddrawings describes examples and does not represent the only examplesthat may be implemented or that are within the scope of the claims. Theterm “example,” when used in this description, mean “serving as anexample, instance, or illustration,” and not “preferred” or“advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand apparatuses are shown in block diagram form in order to avoidobscuring the concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and components described in connectionwith the disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, microprocessors in conjunction with a DSPcore, or any other such configuration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicalpositions. As used herein, including in the claims, the term “and/or,”when used in a list of two or more items, means that any one of thelisted items can be employed by itself, or any combination of two ormore of the listed items can be employed. For example, if a compositionis described as containing components A, B, and/or C, the compositioncan contain A alone; B alone; C alone; A and B in combination; A and Cin combination; B and C in combination; or A, B, and C in combination.Also, as used herein, including in the claims, “or” as used in a list ofitems (for example, a list of items prefaced by a phrase such as “atleast one of” or “one or more of”) indicates a disjunctive list suchthat, for example, a list of “at least one of A, B, or C” means A or Bor C or AB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, flash memory,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, include compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and Blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above are also includedwithin the scope of computer-readable media.

As used herein, the phrase “based on” shall not be construed as areference to a closed set of conditions. For example, an exemplary stepthat is described as “based on condition A” may be based on both acondition A and a condition B without departing from the scope of thepresent disclosure. In other words, as used herein, the phrase “basedon” shall be construed in the same manner as the phrase “based at leastin part on.”

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the scope of thedisclosure. Thus, the disclosure is not to be limited to the examplesand designs described herein but is to be accorded the broadest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A method for providing a communications servicevia a communications satellite, the method comprising: obtaining a firsttransmit beamforming weight set that defines a plurality of firsttransmit spot beams based on a plurality of first antenna feed elementsof the communications satellite; applying, by a transmit beamformingnetwork, the first transmit beamforming weight set to a plurality offirst spot beam signals associated with the plurality of first transmitspot beams to obtain first transmit feed element signals; transmittingthe first transmit feed element signals via the plurality of firstantenna feed elements to generate the plurality of first transmit spotbeams; obtaining a second transmit beamforming weight set that defines aplurality of second transmit spot beams based on the plurality of firstantenna feed elements of the communications satellite; updating, inresponse to a change in orbital position of the communicationssatellite, the transmit beamforming network to apply the second transmitbeamforming weight set; applying, by the transmit beamforming network,the second transmit beamforming weight set to a plurality of second spotbeam signals to obtain second transmit feed element signals; andtransmitting the second transmit feed element signals via the pluralityof first antenna feed elements to generate the plurality of secondtransmit spot beams.
 2. The method of claim 1, further comprising:obtaining a first receive beamforming weight set that defines aplurality of first receive spot beams based on a plurality of secondantenna feed elements of the communications satellite; receiving, viathe plurality of second antenna feed elements, first receive feedelement signals; applying, at a receive beamforming network, the firstreceive beamforming weight set to the first receive feed element signalsto obtain the plurality of first spot beam signals; obtaining a secondreceive beamforming weight set that defines a plurality of secondreceive spot beams based on the plurality of second antenna feedelements; updating, in response to the change in orbital position of thecommunications satellite, the receive beamforming network to apply thesecond receive beamforming weight set; receiving, via the plurality ofsecond antenna feed elements, second receive feed element signals; andapplying, at the receive beamforming network, the second receivebeamforming weight set to the second receive feed element signals toobtain the plurality of second spot beam signals.
 3. The method of claim2, wherein the plurality of second antenna feed elements are the same asthe plurality of first antenna feed elements.
 4. The method of claim 3,wherein each of the plurality of first antenna feed elements isconfigured to operate with a first polarization for receiving the firstreceive feed element signals, and to operate with a second, orthogonalpolarization for transmitting the first transmit feed element signals.5. The method of claim 1, wherein the transmit beamforming network iscoupled between a plurality of beam signal pathways of thecommunications satellite and the plurality of first antenna feedelements.
 6. The method of claim 5, wherein each of the plurality ofbeam signal pathways is coupled with each of the plurality of firstantenna feed elements via the transmit beamforming network.
 7. Themethod of claim 5, wherein each of the plurality of beam signal pathwaysis coupled with a subset of the plurality of first antenna feed elementsvia the transmit beamforming network.
 8. The method of claim 5, whereineach of the plurality of first spot beam signals is associated with oneof the plurality of beam signal pathways.
 9. The method of claim 1,further comprising: storing the first transmit beamforming weight set atthe communications satellite prior to deployment.
 10. The method ofclaim 1, wherein the obtaining the second transmit beamforming weightset comprises receiving, at the communications satellite, the secondtransmit beamforming weight set from a network management entity. 11.The method of claim 1, wherein the obtaining the second transmitbeamforming weight set comprises calculating, at the communicationssatellite, the second transmit beamforming weight set based at least inpart on the change in orbital position of the communications satellite.12. The method of claim 1, wherein the obtaining the second transmitbeamforming weight set comprises selecting, at the communicationssatellite, the second transmit beamforming weight set from a pluralityof beamforming weight sets stored at the communications satellite. 13.The method of claim 1, further comprising: receiving, at thecommunications satellite, a multiplexed transmit signal comprising thefirst transmit feed element signals multiplexed with each other; anddemultiplexing the multiplexed transmit signal to separate each of thefirst transmit feed element signals.
 14. The method of claim 13, whereinthe transmit beamforming network is coupled between a plurality of beamsignal pathways and an access node antenna transmitting the multiplexedtransmit signal to the communications satellite.
 15. The method of claim13, wherein, in the multiplexed transmit signal, the first transmit feedelement signals are time-division multiplexed, frequency-divisionmultiplexed, or code-division multiplexed.
 16. The method of claim 1,wherein: each of the plurality of first transmit spot beams provides thecommunications service to one of a first plurality of cells; and each ofthe plurality of second transmit spot beams provides the communicationsservice to one of a second plurality of cells.
 17. The method of claim16, wherein at least one of the plurality of second spot beam signals isprovided to a cell of the second plurality of cells via a correspondingsecond transmit spot beam with a same bandwidth as a corresponding firsttransmit spot beam, a same frequency as the corresponding first transmitspot beam, a same polarization as the corresponding first transmit spotbeam, a same timing slot sequence as the corresponding first transmitspot beam, or a combination thereof.
 18. The method of claim 16,wherein, for at least one of the second plurality of cells, thecorresponding second transmit spot beam is provided with a same spotbeam coverage area as a corresponding first transmit spot beamassociated with a corresponding one of the first plurality of cells. 19.The method of claim 16, wherein the first plurality of cells is the sameas the second plurality of cells.
 20. The method of claim 1, wherein theplurality of second transmit spot beams provides the communicationsservice over a same satellite coverage area as the plurality of firsttransmit spot beams.
 21. The method of claim 1, wherein the firsttransmit beamforming weight set comprises a first plurality of transmitweight matrices, wherein each of the first plurality of transmit weightmatrices defines a subset of the plurality of first transmit spot beamsassociated with a time slot of a first repeating pattern of time slots.22. The method of claim 21, wherein the second transmit beamformingweight set comprises a second plurality of transmit weight matrices,wherein each of the second plurality of transmit weight matrices definesa subset of the plurality of second transmit spot beams associated witha time slot of a second repeating pattern of time slots.
 23. The methodof claim 22, wherein the first repeating pattern of time slotsassociates each of the time slots with a set of active cells, andwherein the second repeating pattern of time slots associates each ofthe time slots with the set of active cells.
 24. The method of claim 1,further comprising: performing respective frequency conversions on theplurality of first spot beam signals prior to transmitting the firsttransmit feed element signals.
 25. The method of claim 24, furthercomprising: adapting the respective frequency conversions in response tothe change in orbital position of the communications satellite;performing the adapted respective frequency conversions to the pluralityof second spot beam signals prior to transmitting the second transmitfeed element signals.
 26. The method of claim 1, wherein the pluralityof first transmit spot beams are based at least in part on an initialnative antenna pattern, the method further comprising: commanding achange to an adapted native antenna pattern based at least in part onthe change in orbital position of the communications satellite.
 27. Asatellite communications system comprising a communications satellitefor providing a communications service between a plurality of userterminals and a plurality of access node terminals, comprising: meansfor applying a transmit beamforming weight set to a plurality of firstbeam signals to obtain first transmit feed signals, the transmitbeamforming weight set defining a plurality of first transmit beamsbased on a plurality of first antenna feed elements of thecommunications satellite; means for changing, in response to a change inorbital position of the communications satellite, the transmitbeamforming weight set to obtain, from the means for applying, secondtransmit feed signals from second transmit beam signals; and means fortransmitting the first transmit feed signals and the second transmitfeed signals from the communications satellite to generate the pluralityof first transmit beams and a plurality of second transmit beams. 28.The satellite communications system of claim 27, further comprising:means for receiving a plurality of first receive feed signals and aplurality of second receive feed signals; means for applying a receivebeamforming weight set to the plurality of first receive feed signals toobtain the plurality of first beam signals, the receive beamformingweight set defining a plurality of first receive beams based on aplurality of second antenna feed elements of the communicationssatellite; and means for changing, in response to a change in orbitalposition of the communications satellite, the receive beamforming weightset to obtain, from the means for applying the receive beamformingweight set, the second transmit beam signals from second receive feedsignals.
 29. The satellite communications system of claim 28, whereinthe plurality of second antenna feed elements are the same as theplurality of first antenna feed elements.
 30. The satellitecommunications system of claim 29, wherein the means for receiving theplurality of first receive feed signals and the plurality of secondreceive feed signals is configured to operate with a first polarization,and the means for transmitting the first transmit feed signals and thesecond transmit feed signals is configured to operate with a second,orthogonal polarization.
 31. The satellite communications system ofclaim 27, wherein the means for applying the transmit beamforming weightset is coupled between a plurality of beam signal pathways of thecommunications satellite and the plurality of first antenna feedelements.
 32. The satellite communications system of claim 31, whereineach of the plurality of beam signal pathways is coupled with each ofthe plurality of first antenna feed elements via the means for applyingthe transmit beamforming weight set.
 33. The satellite communicationssystem of claim 31, wherein each of the plurality of beam signalpathways is coupled with a subset of the plurality of first antenna feedelements via the means for applying the transmit beamforming weight set.34. The satellite communications system of claim 31, wherein each of theplurality of first beam signals is associated with one of the pluralityof beam signal pathways.
 35. The satellite communications system ofclaim 27, further comprising: means for storing the transmit beamformingweight set at the communications satellite prior to deployment.
 36. Thesatellite communications system of claim 27, further comprising: meansfor receiving, at the communications satellite, the second transmitbeamforming weight set from a network management entity.
 37. Thesatellite communications system of claim 27, further comprising: meansfor calculating, at the communications satellite, the second transmitbeamforming weight set based at least in part on the change in orbitalposition of the communications satellite.
 38. The satellitecommunications system of claim 27, further comprising: means forselecting, at the communications satellite, the second transmitbeamforming weight set from a plurality of beamforming weight setsstored at the communications satellite.
 39. The satellite communicationssystem of claim 27, further comprising: means for receiving, at thecommunications satellite, a multiplexed transmit signal comprising thefirst transmit feed element signals multiplexed with each other; andmeans for demultiplexing the multiplexed transmit signal to separateeach of the first transmit feed element signals.
 40. The satellitecommunications system of claim 39, wherein the means for applying thetransmit beamforming weight set is coupled between a plurality of beamsignal pathways and an access node antenna transmitting the multiplexedtransmit signal to the communications satellite.
 41. The satellitecommunications system of claim 39, wherein, in the multiplexed transmitsignal, the first transmit feed element signals are time-divisionmultiplexed, frequency-division multiplexed, or code-divisionmultiplexed.
 42. The satellite communications system of claim 27,wherein: each of the plurality of first transmit beams provides thecommunications service to one of a first plurality of cells; and each ofthe plurality of second transmit beams provides the communicationsservice to one of a second plurality of cells.
 43. The satellitecommunications system of claim 42, wherein at least one of the secondtransmit beam signals is provided to a cell of the second plurality ofcells via a corresponding second transmit beam with a same bandwidth asa corresponding first transmit beam, a same frequency as thecorresponding first transmit beam, a same polarization as thecorresponding first transmit beam, a same timing slot sequence as thecorresponding first transmit beam, or a combination thereof.
 44. Thesatellite communications system of claim 42, wherein, for at least oneof the second plurality of cells, the corresponding second transmit beamis provided with a same beam coverage area as a corresponding firsttransmit beam associated with a corresponding one of the first pluralityof cells.
 45. The satellite communications system of claim 42, whereinthe first plurality of cells is the same as the second plurality ofcells.
 46. The satellite communications system of claim 27, wherein theplurality of second transmit beams provides the communications serviceover a same satellite coverage area as the plurality of first transmitbeams.
 47. The satellite communications system of claim 27, wherein thefirst transmit beamforming weight set comprises a first plurality oftransmit weight matrices, wherein each of the first plurality oftransmit weight matrices defines a subset of the plurality of firsttransmit beams associated with a time slot of a first repeating patternof time slots.
 48. The satellite communications system of claim 47,wherein the second transmit beamforming weight set comprises a secondplurality of transmit weight matrices, wherein each of the secondplurality of transmit weight matrices defines a subset of the pluralityof second transmit beams associated with a time slot of a secondrepeating pattern of time slots.
 49. The satellite communications systemof claim 48, wherein the first repeating pattern of time slotsassociates each of the time slots with a set of active cells, andwherein the second repeating pattern of time slots associates each ofthe time slots with the set of active cells.
 50. The satellitecommunications system of claim 27, further comprising: means forperforming respective frequency conversions on the plurality of firsttransmit beam signals prior to transmitting the first transmit feedelement signals.
 51. The satellite communications system of claim 50,further comprising: means for adapting the respective frequencyconversions in response to the change in orbital position of thecommunications satellite; means for performing the adapted respectivefrequency conversions to the second transmit beam signals prior totransmitting the second transmit feed element signals.
 52. The satellitecommunications system of claim 27, wherein the plurality of firsttransmit beams are based at least in part on an initial native antennapattern, the satellite communications system further comprising: meansfor commanding a change to an adapted native antenna pattern based atleast in part on the change in orbital position of the communicationssatellite.
 53. A satellite communications system comprising acommunications satellite for providing a communications service betweena plurality of user terminals and a plurality of access node terminals,comprising: a plurality of first antenna feed elements on thecommunications satellite; a plurality of spot beam signal pathways; atransmit beamforming network coupled between the plurality of spot beamsignal pathways and the plurality of first antenna feed elements; and abeam weight processor configured to: obtain a first transmit beamformingweight set that defines a plurality of first transmit spot beams basedon the plurality of first antenna feed elements; configure the transmitbeamforming network to apply the first transmit beamforming weight setto a plurality of first spot beam signals associated with the pluralityof first transmit spot beams to obtain first transmit feed elementsignals for transmission via the plurality of first antenna feedelements; obtain a second transmit beamforming weight set that defines aplurality of second transmit spot beams based on the plurality of firstantenna feed elements of the communications satellite; and configure, inresponse to a change in orbital position of the communicationssatellite, the transmit beamforming network to apply the second transmitbeamforming weight set to second spot beam signals to obtain secondtransmit feed element signals for transmission via the plurality offirst antenna feed elements.
 54. The satellite communications system ofclaim 53, further comprising: a plurality of second antenna feedelements on the communications satellite; and a receive beamformingnetwork coupled between the plurality of spot beam signal pathways andthe plurality of second antenna feed elements; wherein the beam weightprocessor is configured to: obtain a first receive beamforming weightset that defines a plurality of first receive spot beams based on theplurality of second antenna feed elements; configure the receivebeamforming network to apply the first receive beamforming weight set toa plurality of first receive feed element signals to obtain theplurality of first spot beam signals; obtain a second receivebeamforming weight set that defines a plurality of second receive spotbeams based on the plurality of second antenna feed elements; configure,in response to the change in orbital position of the communicationssatellite, the receive beamforming network to apply the second receivebeamforming weight set to a plurality of second receive feed elementsignals to obtain the second spot beam signals.
 55. The satellitecommunications system of claim 54, wherein the plurality of secondantenna feed elements are the same as the plurality of first antennafeed elements.
 56. The satellite communications system of claim 55,wherein each of the plurality of first antenna feed elements isconfigured to operate with a first polarization for receiving the firstreceive feed element signals, and to operate with a second, orthogonalpolarization for transmitting the first transmit feed element signals.57. The satellite communications system of claim 53, wherein thetransmit beamforming network is coupled between the plurality of spotbeam signal pathways and the plurality of first antenna feed elements.58. The satellite communications system of claim 57, wherein each of theplurality of spot beam signal pathways is coupled with each of theplurality of first antenna feed elements via the transmit beamformingnetwork.
 59. The satellite communications system of claim 57, whereineach of the plurality of spot beam signal pathways is coupled with asubset of the plurality of first antenna feed elements via the transmitbeamforming network.
 60. The satellite communications system of claim57, wherein each of the plurality of first spot beam signals isassociated with one of the plurality of spot beam signal pathways. 61.The satellite communications system of claim 53, wherein the beam weightprocessor is configured to: store the first transmit beamforming weightset at the communications satellite prior to deployment.
 62. Thesatellite communications system of claim 53, wherein the beam weightprocessor is configured to: receive, at the communications satellite,the second transmit beamforming weight set from a network managemententity.
 63. The satellite communications system of claim 53, wherein thebeam weight processor is configured to: calculate, at the communicationssatellite, the second transmit beamforming weight set based at least inpart on the change in orbital position of the communications satellite.64. The satellite communications system of claim 53, wherein the beamweight processor is configured to: select, at the communicationssatellite, the second transmit beamforming weight set from a pluralityof beamforming weight sets stored at the communications satellite. 65.The satellite communications system of claim 53, wherein thecommunications satellite is configured to: receive a multiplexedtransmit signal comprising the first transmit feed element signalsmultiplexed with each other; and demultiplex the multiplexed transmitsignal to separate each of the first transmit feed element signals. 66.The satellite communications system of claim 65, wherein the transmitbeamforming network is coupled between a plurality of beam signalpathways and an access node antenna transmitting the multiplexedtransmit signal to the communications satellite.
 67. The satellitecommunications system of claim 65, wherein, in the multiplexed transmitsignal, the first transmit feed element signals are time-divisionmultiplexed, frequency-division multiplexed, or code-divisionmultiplexed.
 68. The satellite communications system of claim 53,wherein: each of the plurality of first transmit spot beams provides thecommunications service to one of a first plurality of cells; and each ofthe plurality of second transmit spot beams provides the communicationsservice to one of a second plurality of cells.
 69. The satellitecommunications system of claim 68, wherein at least one of the secondspot beam signals is provided to a cell of the second plurality of cellsvia a corresponding second transmit spot beam with a same bandwidth as acorresponding first transmit spot beam, a same frequency as thecorresponding first transmit spot beam, a same polarization as thecorresponding first transmit spot beam, a same timing slot sequence asthe corresponding first transmit spot beam, or a combination thereof.70. The satellite communications system of claim 68, wherein, for atleast one of the second plurality of cells, the corresponding secondtransmit spot beam is provided with a same spot beam coverage area as acorresponding first transmit spot beam associated with a correspondingone of the first plurality of cells.
 71. The satellite communicationssystem of claim 68, wherein the first plurality of cells is the same asthe second plurality of cells.
 72. The satellite communications systemof claim 53, wherein the plurality of second transmit spot beamsprovides the communications service over a same satellite coverage areaas the plurality of first transmit spot beams.
 73. The satellitecommunications system of claim 53, wherein the first transmitbeamforming weight set comprises a first plurality of transmit weightmatrices, wherein each of the first plurality of transmit weightmatrices defines a subset of the plurality of first transmit spot beamsassociated with a time slot of a first repeating pattern of time slots.74. The satellite communications system of claim 73, wherein the secondtransmit beamforming weight set comprises a second plurality of transmitweight matrices, wherein each of the second plurality of transmit weightmatrices defines a subset of the plurality of second transmit spot beamsassociated with a time slot of a second repeating pattern of time slots.75. The satellite communications system of claim 74, wherein the firstrepeating pattern of time slots associates each of the time slots with aset of active cells, and wherein the second repeating pattern of timeslots associates each of the time slots with the set of active cells.76. The satellite communications system of claim 53, wherein the beamweight processor is configured to: configure the transmit beamformingnetwork to perform respective frequency conversions on the plurality offirst spot beam signals prior to transmitting the first transmit feedelement signals.
 77. The satellite communications system of claim 76,wherein the beam weight processor is configured to: adapting therespective frequency conversions in response to the change in orbitalposition of the communications satellite; and configure the transmitbeamforming network to perform the adapted respective frequencyconversions to the second spot beam signals prior to transmitting thesecond transmit feed element signals.
 78. The satellite communicationssystem of claim 77, wherein the plurality of first transmit spot beamsare based at least in part on an initial native antenna pattern, and thebeam weight processor is configured to: command a change to an adaptednative antenna pattern based at least in part on the change in orbitalposition of the communications satellite.